intermediate vessel

19 LETTERS · STARTS WITH I

intermediate vessel is a valid 19-letter word worth 24 points in Scrabble and 28 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS

I1N1T1E1R1M3E1D2I1A1T1E1V4E1S1S1E1L1

1 + 1 + 1 + 1 + 1 + 3 + 1 + 2 + 1 + 1 + 1 + 1 + 0 + 4 + 1 + 1 + 1 + 1 + 1 =24 PTS

DOUBLE WORD → 48TRIPLE WORD → 72

MEANING

What does intermediate vessel mean?