blink

Concise Oxford English Dictionary © 2008 Oxford University Press:
blink/blɪŋk/

▶verb

• 1 shut and open the eyes quickly.

• 2 [usu. with neg.] react with surprise or disapproval: he doesn't blink at the unsavoury aspects of his subject.

• 3 (of a light) flash on and off.

▶noun

• 1 an act of blinking.

• 2 a momentary gleam of light.

– phrases
in the blink of an eye (or in a blink) very quickly.
on the blink informal (of a machine) not working properly; out of order.

– origin ME (in senses ‘deceive’, ‘flinch’, ‘open the eyes after sleep’): from blenk, Scots var. of blench1.