closing error

13 LETTERS · STARTS WITH C

closing error is a valid 13-letter word worth 15 points in Scrabble and 19 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS

C3L1O1S1I1N1G2E1R1R1O1R1

3 + 1 + 1 + 1 + 1 + 1 + 2 + 0 + 1 + 1 + 1 + 1 + 1 =15 PTS

DOUBLE WORD → 30TRIPLE WORD → 45

MEANING

What does closing error mean?