/brong"koh/ , n. , pl. broncos .
a range pony or mustang of the western U.S., esp. one that is not broken or is imperfectly broken.
Also, bronc, broncho .
[ 1865-70, Amer.; potro bronco untamed colt (in MexSp: wild horse, half-tamed horse); bronco, appar. nasalized var. of L broccus; see BROACH ]