differential recorder

21 LETTERS · STARTS WITH D

differential recorder is a valid 21-letter word worth 30 points in Scrabble and 33 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS

D2I1F4F4E1R1E1N1T1I1A1L1R1E1C3O1R1D2E1R1

2 + 1 + 4 + 4 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 0 + 1 + 1 + 3 + 1 + 1 + 2 + 1 + 1 =30 PTS

DOUBLE WORD → 60TRIPLE WORD → 90

MEANING

What does differential recorder mean?