1the hind part of the body of a mammal or the lower back of a bird:the harrier is distinguished by its prominent white rumphe slapped the horse on the rump [mass noun]:a medium-rare slice of rump
chiefly humorous a person’s buttocks:he removed his hand from Shirley’s rump
2a small or unimportant remnant of something originally larger:once the profitable enterprises have been sold the unprofitable rump will be left [as modifier]:the rump Yugoslavia