quaternary ammonium compound
quaternary ammonium compound definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
any of a class of compounds in which the four hydrogen atoms of the ammonium radical are replaced by other groups, generally organic radicals: used as solvents, disinfectants, etc.
quaternary ammonium compound definition by American Heritage Dictionary
Any of a group of compounds in which a central nitrogen atom is joined to four organic radicals and one acid radical, used as antiseptics, solvents, and emulsifying agents.