chain armor

NOUN /tʃeɪn_'ɑrmər/
11 LETTERS · STARTS WITH C

chain armor is a valid 11-letter word worth 17 points in Scrabble and 19 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS
C3H4A1I1N1A1R1M3O1R1
3 + 4 + 1 + 1 + 1 + 0 + 1 + 1 + 3 + 1 + 1 =17 PTS
DOUBLE WORD → 34TRIPLE WORD → 51
MEANING

What does chain armor mean?