Definition from Wiktionary, the free dictionary
- (chiefly horses) of inferior breeding
1902, Frank Sherman Peer, Cross country with horse and hound:
- I prefer both sire and dam to be well-bred, but a well-bred mare and an underbred horse will produce a faster animal than a thoroughbred horse and an underbred mare.
- lacking in manners or finesse
- (breeding): thoroughbred