Yes, sags is a Scrabble word!
...and is worth 5 points in Scrabble, and 6 points in Words with Friends
sags
Verb
1. Droop, sink, or settle from or as if from pressure or loss of tautness
2. Cause to sag
Noun
1. A shape that sags
What Scrabble words can I make with the letters in sags?
3 Letter Words
2 Letter Words