The state of being twitchy, physical restlessness. / The state of being nervous and unsettled; edginess.

A brief, small (sometimes involuntary) movement out of place and then back again; a spasm. / (informal) Action of spotting or seeking out a bird, especially a rare one.

(intransitive) To perform a twitch; spasm. / (transitive) To cause to twitch; spasm. / (transitive) To jerk sharply and briefly. / (obsolete) To exert oneself.

couch grass (Elymus repens; a species of grass, often considered as a weed)

The sound of a succession of chirps as uttered by birds. / A tremulous broken sound. / A slight trembling of the nerves.

(intransitive) To utter a succession of chirps. / (intransitive, transitive) (of a person) To talk in an excited or nervous manner. / To make the sound of a half-suppressed laugh; to titter; to giggle.

A small passerine bird, Linaria flavirostris (syn. Carduelis flavirostris), that breeds in northern Europe and across central Asia.

present participle of twitch

The motion of something that twitches. / (birdwatching) Compulsive birdwatching by people (twitchers) who travel long distances to see rare species.

That twitches.