prophylactic device

NOUN
19 LETTERS · STARTS WITH P

prophylactic device is a valid 19-letter word worth 38 points in Scrabble and 43 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS
P3R1O1P3H4Y4L1A1C3T1I1C3D2E1V4I1C3E1
3 + 1 + 1 + 3 + 4 + 4 + 1 + 1 + 3 + 1 + 1 + 3 + 0 + 2 + 1 + 4 + 1 + 3 + 1 =38 PTS
DOUBLE WORD → 76TRIPLE WORD → 114
MEANING

What does prophylactic device mean?