Yes, buff is a Scrabble word!

Verb

1. Strike, beat repeatedly

2. Polish and make shiny

Adjective

1. Of the yellowish-beige color of buff leather

Noun

1. An ardent follower and admirer

2. A soft thick undyed leather from the skins of e.g. buffalo or oxen

3. Bare skin; naked

4. A medium to dark tan color

5. An implement consisting of soft material mounted on a block; used for polishing (as in manicuring)