interior drainage

17 LETTERS · STARTS WITH I

interior drainage is a valid 17-letter word worth 18 points in Scrabble and 21 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS

I1N1T1E1R1I1O1R1D2R1A1I1N1A1G2E1

1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 0 + 2 + 1 + 1 + 1 + 1 + 1 + 2 + 1 =18 PTS

DOUBLE WORD → 36TRIPLE WORD → 54

MEANING

What does interior drainage mean?