Yes, duck is a Scrabble word!
...and is worth 11 points in Scrabble, and 13 points in Words with Friends
duck
Verb
1. To move (the head or body) quickly downwards or away
2. Submerge or plunge suddenly
3. Dip into a liquid
4. Avoid or try to avoid fulfilling, answering, or performing (duties, questions, or issues)
Noun
1. Small wild or domesticated web-footed broad-billed swimming bird usually having a depressed body and short legs
2. (cricket) a score of nothing by a batsman
3. Flesh of a duck (domestic or wild)
4. A heavy cotton fabric of plain weave; used for clothing and tents
What Scrabble words can I make with the letters in duck?
3 Letter Words