historical error

16 LETTERS · STARTS WITH H

historical error is a valid 16-letter word worth 20 points in Scrabble and 21 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS

H4I1S1T1O1R1I1C3A1L1E1R1R1O1R1

4 + 1 + 1 + 1 + 1 + 1 + 1 + 3 + 1 + 1 + 0 + 1 + 1 + 1 + 1 + 1 =20 PTS

DOUBLE WORD → 40TRIPLE WORD → 60

MEANING

What does historical error mean?