Yes, purr is a Scrabble word!
...and is worth 6 points in Scrabble, and 8 points in Words with Friends
purr
Verb
1. Make a soft swishing sound
2. Indicate pleasure by purring; characteristic of cats
Noun
1. A low vibrating sound typical of a contented cat
What Scrabble words can I make with the letters in purr?
3 Letter Words
2 Letter Words