subsonic speed

14 LETTERS · STARTS WITH S

subsonic speed is a valid 14-letter word worth 20 points in Scrabble and 25 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS

S1U1B3S1O1N1I1C3S1P3E1E1D2

1 + 1 + 3 + 1 + 1 + 1 + 1 + 3 + 0 + 1 + 3 + 1 + 1 + 2 =20 PTS

DOUBLE WORD → 40TRIPLE WORD → 60

MEANING

What does subsonic speed mean?