/ Dictionary / Index P pyrimidine: Meaning and Definition of Find definitions for: py•rim•i•dine Pronunciation: (pī-rim'i-dēn", pi-, pir'u-mi-dēn", -din), [key] — n. Biochem. a heterocyclic compound, CHN, that is the basis of several important biochemical substances. one of several pyrimidine derivatives, esp. the bases cytosine, thymine, and uracil, which are fundamental constituents of nucleic acids. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: pyrimidine (Thesaurus) pyrimethamine Pyriphlegethon Related Content Daily Word Quiz: fervor Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language