In reporting on the BP oil spill, the media has at times taken liberties in the use of unexplained technical terminology. In the interests of helping readers more easily follow the environmental disaster still unfolding in the Gulf of Mexico, here is a basic glossary of oil spill-related terms:

(noun, pl.) A wall or barrier of sand, ordinarily used to protect against flooding in coastal regions, but now being used to stop oil from washing up on beaches in Gulf Coast states.
In context: "[Gov. Bobby Jindal] called on the federal government to approve a plan to build sand berms to protect the bayou country." — New York Times

Blowout preventer
(noun) Known in industry circles as a BOP, this is essentially an enormous safety valve that automatically seals the well if there is a problem. It failed to work on the Deepwater Horizon rig.
In context: "BP investigators are trying to determine whether any modifications to the blowout preventer that apparently failed to halt the Gulf of Mexico oil spill may have affected its operation" — Houston Chronicle

(noun, pl.) Plastic or cloth flotation devices, linked together in a chain, designed to stop surface oil slicks from washing inland. One of the methods local communities are using to prevent oil coming to shore.
In context: "At Blind Bay Louisiana and elsewhere, oil has drifted under or over the booms onto land." — Reuters

Cement plug
(noun) A layer of cement placed inside the well during drilling to prevent methane gas from leaking up the pipe. An incorrectly installed cement plug is at the center of the dispute between well owner BP, rig owner Transocean and contractor Halliburton over what caused the explosion.
In context:
"One focus of the Senate hearing into the Deepwater Horizon disaster was why the final step in the cementing process—putting a cement plug in the well more than a mile below the sea surface—wasn't performed." — Wall Street Journal

Containment cap
(noun) The custom-built collection device that was placed over the gushing oil well on June 3. The bell-shaped structure is engineered to create a seal over an open pipe atop the blowout preventer, and funnel leaking oil up to a tanker ship floating above. BP says the containment cap is now trapping between 11,000 and 15,000 barrels of oil a day.
In context: "A newly-installed containment cap on the stricken BP rig is helping to limit the leak" - Press Association

(noun, pl.) Chemicals applied directly to spilled oil to break up slicks and make oil disperse into the water. BP has been using a dispersant called Corexit, but the EPA is concerned about the chemical's toxicity and has asked BP to find an alternative.
In context: "BP has already dumped 700,000 gallons of the dispersant into the sea." — ABC News

Drilling mud
(noun) A high-density slurry composed of clay, water, minerals and chemicals that is pumped into a well to exert downward pressure on the gas and oil below and prevent them gushing out. It is also used to cool and lubricate wells during drilling.
In context: "After an 18-hour delay Thursday to assess its efforts and bring in more materials, BP resumed pumping heavy drilling mud into the blown-out well 5,000 feet underwater in a procedure known as a top kill." — AP

(verb) Method by which oil can be determined to have originated from a particular source. Also referred to as hydrocarbon profiling.
In context: "NOAA has also been fingerprinting the oil to determine if it is from the Deepwater Horizon spill or some other oil that may emerge from from natural oil seeps on the seafloor" - Environmental News Service

Junk shot
(noun) Another temporary way to plug the oil leak, by injecting "solid rubbery and fibrous material" into the head of the broken well with the intention of clogging the pipe and stanching the flow. It was one of the catalogue of failed attempts to plug the leak in May.
In context: "The goal of the junk shot is to force-feed the preventer, the device that failed when the disaster unfolded on April 20." — New York Times

Liability cap
(noun) The financial cap on the amount of damages an oil company is legally required to pay for an oil spill. It is currently set at $75 million, but Washington lawmakers are proposing legislation to raise the liability cap for small spills, and abolish it for larger ones.
In context: "Legislation has been introduced in Congress that would blow the lid off the liability cap and raise it to $10 billion" - Marketplace Report

Loop Current
(noun) The "ribbon" of warm ocean water that flows from the Caribbean sea, loops clockwise around the Gulf of Mexico, and then washes into the Atlantic through the Florida straits. Oil from the spill has now been sucked into it.
In context: "The slick is now being swept toward Florida's tourist beaches and fragile coral reefs by the powerful Loop Current." — Vancouver Sun

(acronym) Lower Marine Riser Package. The section of the broken blowout preventer upon which a temporary containment cap has now been fitted.
In context:"The cap sits on the BOP's lower marine riser package (LMRP) section" - BBC

(acronym) The Minerals Management Service, the federal agency that oversees offshore drilling. Widely criticized for failing to regulate the Deepwater Horizon rig. Soon to be broken up into three divisions in response to the disaster.
In context: "President Obama has said MMS has been too cozy with the industry, and critics say oil and gas companies have too much say over the federal regulations." — New York Times

(acronym) The National Oceanographic and Atmospheric Administration. The federal agency which monitors the condition of the oceans and the atmosphere.
In context: "In congressional testimony on Wednesday, leading scientists criticized the NOAA for 'failing to conduct adequate scientific analysis of the spill and allowing BP to obscure the spill's true scope.'" — Politics Daily

Relief well
(noun) A secondary well drilled to intersect the leaking main well, allowing engineers to intercept the oil flow from the reservoir below and pump in cement and heavy fluids to stop the leak. It is considered the most surefire method to permanently stop the leak, but will take months to complete.
In context: BP has "begun to drill a relief well a half-mile away from the leak and positioned to intercept it at 13,000 feet below the seabed." — AOL News

Riser pipe
(noun) The pipe that connects an underwater wellhead to the drilling rig floating on the surface of the ocean above. In the case of the Deepwater Horizon, the riser — now crumpled on the ocean floor — was approximately a mile long.
In context: "A drill pipe currently trapped inside the riser has reduced the flow area by an additional 10 percent." — BP statement

Riser insertion tube tool
(noun) Another temporary solution for plugging up an oil spill. "Essentially an industrial-size catheter," it partially blocks the flow of oil coming out of the riser pipe. Has been successfully stemming some of the oil all this week. Also known as a ... RITT.
In context: "The volume of oil and gas being collected by the riser insertion tube tool (RITT) containment system at the end of the leaking riser is estimated to be about 3,000 barrels a day." — Business Financial Newswire

(noun, pl.) Boats that suck in oily water off the surface of slick. One of the methods local communities are using to clean their waters.
In context: "BP says that skimmers have already sucked up more than 14 million gallons of oily water. The water portion of that is considered contaminated and has to be handled with care." — NPR

Tar balls 
(noun) Small, dark-colored pieces of weathered oil that washes up on a beach. The NOAA says we will recognize them as the coin-size oil chunks that "stick to our feet when we go to the beach."
In context: "There is no magic trick to making tar balls disappear. Once tar balls hit the beaches, they may be picked up by hand or by beach-cleaning machinery." — NOAA

Top hat
(noun) A two-ton containment device that, in theory, would have capped off the oil. Introduced as an option after a larger containment device failed, but was ignored in favor of the riser insertion tube.
In context: "BP is abandoning—at least for now—plans to use to the 'top hat' containment dome to curtail the spill." — Newsweek

Top kill
(noun) Another temporary method of sealing the oil well. Essentially, it involves pumping dense mud into the blowout preventer under such high pressure that it forces the leaking oil back into the ground. The manuever was attempted in late May, but failed.
In context: "With BP's latest method, called 'top kill,' the company thinks it has finally figured out a way to plug the leak." — WDSU

(verb) The physical and chemical process that changes the oil from a slick to tar balls spread over a large area.
In context: "Dilution and weathering would reduce [the oil slick] to some combination of thin strips of mayonnaise-like ooze mixed with tar balls." — Miami Herald

Well bore
(noun) A hole drilled for the purpose of extracting oil. In other words, the actual hole in the sea floor.
In context:
BP is "considering several methods of shutting down the well, including a "dynamic kill" by inserting fluids and drilling "mud" into the well bore ." — Daily Herald

Well casing
(noun) A large pipe inserted into the well bore for structural reinforcement and to prevent oil from leaking out of the well. (Also referred to as "casing" or "casing pipe.")
In context: "BP engineers expressed concerns that the metal well casing the company wanted to use might collapse under high pressure." — The Sydney Morning Herald

Well head
(noun) The component at the surface of a well bore on which the apparatus for extracting the oil is attached. This is the component from which the oil is leaking. The blowout preventer is at the well head.
In context: "Reports say 210,000 gallons of oil have leaked daily into the Gulf of Mexico from this damaged well head." — USA Today

This article was originally published May 21