Dictionary.com
definitions

ternary form

noun
  1. a musical form in three sections, with the third usually an exact repetition of the first.

Origin of ternary form

First recorded in 1895–1900
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
British Dictionary definitions for ternary form

ternary form

noun
  1. a musical structure consisting of two contrasting sections followed by a repetition of the first; the form abaAlso called: song form
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012