activated charcoal

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Highly absorbent carbon obtained by heating granulated charcoal to exhaust contained gases, resulting in a very porous form with a large surface area. It is used chiefly for purifying gases by adsorption, solvent recovery, or deodorization and as an antidote to certain poisons.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun chemistry activated carbon

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun powdered or granular carbon used for purifying by adsorption; given orally (as a slurry) it is an antidote for some kinds of poisons