A tank or vessel designed to cook a liquid or extract or digest solids in suspension; the cooker usually contains a source of heat; and is fitted with an agitator.
Usually a spoon or something made of metal used by some addicts to heat up a mixture of heroin and water to disolve the heroin. As Andrea pointed out, many addicts feeltheydo not have to "cook" heroin because of the better quality. Not unusually addicts would "cook" their heroin by using a lighter or match to heat a spoon.
Fireless steam or air loco. Usually used in mine or other short-run industrial site where the tank can be charged often. AKA Thermos bottle. See Fireless Locomotive.