unison interval

15 LETTERS · STARTS WITH U

unison interval is a valid 15-letter word worth 17 points in Scrabble and 23 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS

U1N1I1S1O1N1I1N1T1E1R1V4A1L1

1 + 1 + 1 + 1 + 1 + 1 + 0 + 1 + 1 + 1 + 1 + 1 + 4 + 1 + 1 =17 PTS

DOUBLE WORD → 34TRIPLE WORD → 51

MEANING

What does unison interval mean?