From The Collaborative International Dictionary of English v.0.48 [gcide]:
Flinch \Flinch\, v. i. [imp. & p. p. Flinched; p. pr. & vb. n.
Flinching.] [Prob. fr. OE. flecchen to waver, give way, F.
fl['e]chir, fr. L. flectere to bend; but prob. influenced by
E. blench. Cf. Flex.]
1. To withdraw from any suffering or undertaking, from pain
or danger; to fail in doing or perserving; to show signs
of yielding or of suffering; to shrink; to wince; as, one
of the parties flinched from the combat.
[1913 Webster]
A child, by a constant course of kindness, may be
accustomed to bear very rough usage without
flinching or complaining. --Locke.
[1913 Webster]
2. (Croquet) To let the foot slip from a ball, when
attempting to give a tight croquet.
[1913 Webster]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Flinch \Flinch\, n.
The act of flinching.
[1913 Webster]
From WordNet (r) 3.0 (2006) [wn]:
flinch
n 1: a reflex response to sudden pain [syn: wince, flinch]
v 1: draw back, as with fear or pain; "she flinched when they
showed the slaughtering of the calf" [syn: flinch,
squinch, funk, cringe, shrink, wince, recoil,
quail]