rhomboid muscle

NOUN
15 LETTERS · STARTS WITH R

rhomboid muscle is a valid 15-letter word worth 26 points in Scrabble and 31 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS
R1H4O1M3B3O1I1D2M3U1S1C3L1E1
1 + 4 + 1 + 3 + 3 + 1 + 1 + 2 + 0 + 3 + 1 + 1 + 3 + 1 + 1 =26 PTS
DOUBLE WORD → 52TRIPLE WORD → 78
MEANING

What does rhomboid muscle mean?