Other forms: twitching, twitches
To twitch is to make a small sudden movement you did not choose to make. An eyelid that twitches all afternoon, the paw of a sleeping dog, the corner of a mouth twitching in someone trying not to laugh.
Twitch is tiny and out of your control — that is the whole point of it, and it is why a twitching eye reads as tiredness or nerves. It takes an object when you move something with one small sharp pull: twitch the curtain aside to see who is at the gate. The noun is a twitch, as in "a nervous twitch", and twitchy means jumpy, on edge, waiting for something to go wrong. In British English a twitcher is a birdwatcher who travels miles to see a rare bird, which has nothing to do with nerves at all.
1verbcannotTo make a small sudden movement that you cannot control.
“His left eye twitched whenever he was tired.”
2verbtwitchTo pull something with a small sharp movement.
“She twitched the curtain back an inch and looked out.”
3nounsuddenA small sudden movement made without control.
“There was a twitch at the corner of his mouth.”
Too few real examples of this word to estimate which sense is commonest.
Twitch started life as pinching. Old English twiċċan goes back to Proto-West Germanic *twikkijan, "to nail, pin, fasten, clasp, pinch", and its closest English relative is tweak. German zwicken, "to pinch", is the same word on the other side of the North Sea. A twitch is what a small sharp pinch looks like from the outside.
Proto-West Germanic
*twikkijan — to nail, pin, fasten, clasp, pinch
Old English
*twiċċan
Middle English
twicchen
English, today
twitch
From Middle English twicchen, from Old English twiċċan, from Proto-West Germanic twikkijan (“to nail, pin, fasten, clasp, pinch”). Cognate with English tweak, Low German twikken, German Low German twicken (“to pinch, pinch off”), zweckōn and gizwickan (> German zwicken (“to pinch”)).
Etymology from Wiktionary, CC BY-SA