counterrotating propeller

25 LETTERS · STARTS WITH C

counterrotating propeller is a valid 25-letter word worth 31 points in Scrabble and 40 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS

C3O1U1N1T1E1R1R1O1T1A1T1I1N1G2P3R1O1P3E1L1L1E1R1

3 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 2 + 0 + 3 + 1 + 1 + 3 + 1 + 1 + 1 + 1 + 1 =31 PTS

DOUBLE WORD → 62TRIPLE WORD → 93

MEANING

What does counterrotating propeller mean?