the part of a cannon behind the bore

a person's buttocks

relating to or denoting presentation of a fetus in which the buttocks, rump, or legs are nearest the cervix and emerge first at birth

breech presentation occurs in up to 3 per cent of pregnancies at term

my second son was breech and my doctor recommended a planned C-section

dress (a boy) in breeches after he had been in petticoats since birth

in those days it wasn't customary to breech a boy until he was about four