colour tv tube

NOUN
14 LETTERS · STARTS WITH C

colour tv tube is a valid 14-letter word worth 19 points in Scrabble and 25 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS
C3O1L1O1U1R1T1V4T1U1B3E1
3 + 1 + 1 + 1 + 1 + 1 + 0 + 1 + 4 + 0 + 1 + 1 + 3 + 1 =19 PTS
DOUBLE WORD → 38TRIPLE WORD → 57
MEANING

What does colour tv tube mean?