Yes, reef is a Scrabble word!

Verb

1. Lower and bring partially inboard

2. Roll up (a portion of a sail) in order to reduce its area

3. Reduce (a sail) by taking in a reef

Noun

1. A submerged ridge of rock or coral near the surface of the water

2. A rocky region in the southern Transvaal in northeastern South Africa; contains rich gold deposits and coal and manganese

3. One of several strips across a sail that can be taken in or rolled up to lessen the area of the sail that is exposed to the wind