1. A group or set of three of one kind.
2. One of three children born at one birth.
3. A group of three lines of verse.
4. Music. A group of three notes having the time value of two notes of the same kind. Also called tercet.
5. Physics. A multiplet with three components.
6. Genetics. A unit of three successive nucleotides in a molecule of DNA or RNA that codes for a specific amino acid; a codon or anticodon.

[TRIPL(E) + (DOUBL)ET.]

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.