/ Dictionary / Index P piperacillin: Meaning and Definition of Find definitions for: pi•per•a•cil•lin Pronunciation: (pī-per"u-sil'in), [key] — n. Pharm. a broad-spectrum semisynthetic penicillin, CHNNaO, used against certain susceptible Gram-positive and Gram-negative bacteria and certain anaerobes, esp. P. aeruginosa. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: piperacillin (Thesaurus) piperaceous pipe rack Related Content Daily Word Quiz: gregarious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language