To close one's eyes quickly and involuntarily; to blink.
To blink with only one eye as a message, signal, or suggestion, usually with an implication of conspiracy. (When transitive, the object may be the eye being winked, or the message being conveyed.)
From Middle English winken and Middle English winken, from Old English *wincan and wincian, from Proto-Germanic *winkaną ("to move side to side, sway"), *winkōn, from Proto-Indo-European *weng- ("to bow, bend, arch, curve"). Cognate with Middle Low German winken ("to blink, wink"), German winken ("to nod, beckon, make a sign"). Related also to Saterland Frisian wäänke, Dutch wenken ("to beckon, motion"), Latin vacillare ("sway"), Lithuanian véngti ("to swerve, avoid"), Albanian vang ("tire, felloe"), Sanskrit वञ्चति ("he swaggers").