benzalkonium chloride

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

• noun A yellow-white powder prepared in an aqueous solution and used as a detergent, fungicide, bactericide, and spermicide.

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

• noun chemistry A nitrogenous cationic surface-acting agent of the quaternary ammonium group, used as a biocide, as a cationic surfactant and as a phase transfer agent in the chemical industry.