/ Dictionary / Index P polymyxin: Meaning and Definition of Find definitions for: pol•y•myx•in Pronunciation: (pol"ē-mik'sin), [key] — n. Pharm. any of various polypeptide antibiotics derived from Bacillus polymyxa. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: polymyxin (Thesaurus) polymyalgia rheumatica Polynesia Related Content Daily Word Quiz: careening Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language