Definition of "penicillin" [pen•i•cil•lin]

• Any of a group of broad-spectrum antibiotic drugs obtained from penicillium molds or produced synthetically, most active against gram-positive bacteria and used in the treatment of various infections and diseases. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "I'd rather be nice and rotten than covered with those whiskers of mold, although the penicillin is a pretty good preservative."
• "The disease, once easily killed with a shot of penicillin, is increasingly becoming drug-resistant."
• "A shot of penicillin is a cheap cure, but many people never experience specific symptoms and the disease remains undiagnosed."