noun Western U.S.
a horse or pony used in herding cattle.
Before X Was X: The Dark Horse Story Of The 24th LetterSince its inception, the letter X has struggled to establish its own identity, so it may be no coincidence that X is commonly used to represent the unknown in both language and mathematics. But, how was it created?
Origin of stock horse
First recorded in 1860–65
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Examples from the Web for stock horse
Once I stopped to look at Jim: I just sat back and the mare 'propped'—she'd been a stock-horse, and was used to 'cutting-out'.Joe Wilson and His Mates|Henry Lawson