Yes, rump is a Scrabble word!
...and is worth 8 points in Scrabble, and 11 points in Words with Friends
rump
Noun
1. The part of an animal that corresponds to the human buttocks
2. Fleshy hindquarters; behind the loin and above the round
3. The fleshy part of the human body that you sit on
What Scrabble words can I make with the letters in rump?
3 Letter Words
2 Letter Words