displacement unit

NOUN
17 LETTERS · STARTS WITH D

displacement unit is a valid 17-letter word worth 23 points in Scrabble and 30 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS
D2I1S1P3L1A1C3E1M3E1N1T1U1N1I1T1
2 + 1 + 1 + 3 + 1 + 1 + 3 + 1 + 3 + 1 + 1 + 1 + 0 + 1 + 1 + 1 + 1 =23 PTS
DOUBLE WORD → 46TRIPLE WORD → 69
MEANING

What does displacement unit mean?