Yes, rook is a Scrabble word!
...and is worth 8 points in Scrabble, and 8 points in Words with Friends
rook
Verb
1. Deprive of by deceit
Noun
1. (chess) the piece that can move any number of unoccupied squares in a direction parallel to the sides of the chessboard
2. Common gregarious Old World bird about the size and color of the American crow
What Scrabble words can I make with the letters in rook?
3 Letter Words
2 Letter Words