reflex action

NOUN
13 LETTERS · STARTS WITH R

reflex action is a valid 13-letter word worth 24 points in Scrabble and 27 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS
R1E1F4L1E1X8A1C3T1I1O1N1
1 + 1 + 4 + 1 + 1 + 8 + 0 + 1 + 3 + 1 + 1 + 1 + 1 =24 PTS
DOUBLE WORD → 48TRIPLE WORD → 72
MEANING

What does reflex action mean?