serratus muscles

NOUN
16 LETTERS · STARTS WITH S

serratus muscles is a valid 16-letter word worth 19 points in Scrabble and 24 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS
S1E1R1R1A1T1U1S1M3U1S1C3L1E1S1
1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 0 + 3 + 1 + 1 + 3 + 1 + 1 + 1 =19 PTS
DOUBLE WORD → 38TRIPLE WORD → 57
MEANING

What does serratus muscles mean?