ill breeding, ˈill-ˈbreeding [ill a. + breeding vbl.n.] Bad or inferior breeding or bringing up; hence, Bad manners, rudeness. 1800E. Hervey Mourtray Fam. II. 136 Declamations against the ill-breeding of modern young men.1819Byron Juan i. clxxiv, To say the best, it was extreme ill-breeding.