A single-ringed, crystalline organic base, C4H4N2, that forms uracil, cytosine, or thymine and is the parent compound of many drugs, including the barbiturates.
Any of several organic compounds derived from or structurally related to pyrimidine, especially the nitrogen bases uracil, cytosine, and thymine.
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.