Yes, mat is a Scrabble word!
...and is worth 5 points in Scrabble, and 6 points in Words with Friends
mat
Verb
1. Twist together or entwine into a confusing mass
2. Change texture so as to become matted and felt-like
Adjective
1. Not reflecting light; not glossy
Noun
1. A thick flat pad used as a floor covering
2. Mounting consisting of a border or background for a picture
3. Sports equipment consisting of a piece of thick padding on the floor for gymnastic sports
4. A mass that is densely tangled or interwoven
5. A master's degree in teaching
6. The property of having little or no contrast; lacking highlights or gloss
7. A small pad of material that is used to protect surface from an object placed on it
What Scrabble words can I make with the letters in mat?
3 Letter Words
2 Letter Words