The Collaborative International Dictionary
Roach-backed
Roach-backed \Roach"-backed`\, a. Having a back like that of roach; -- said of a horse whose back a convex instead of a concave curve.
Wiktionary
roach-backed
a. (context of a horse English) Having a convex back rather than a concave one.
Usage examples of "roach-backed".
They were spindly-legged beasts, many of them roach-backed, the spine curving upwards thus making them uncomfortable to ride.