The Collaborative International Dictionary of English v.0.48:
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.
A child, by a constant course of kindness, may be
accustomed to bear very rough usage without
flinching or complaining. --Locke.
2. (Croquet) To let the foot slip from a ball, when
attempting to give a tight croquet.