Pronunciation: (pī-rim'i-dēn", pi-, pir'u-mi-dēn", -din), [key]
1. a heterocyclic compound, C4H4N2, that is the basis of several important biochemical substances.
2. 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.