means A short message posted on the platform formerly called Twitter, or the small chirping sound a bird makes.

from Originally an imitative word — "tweet" is the human attempt to spell a birdsong, a cousin of "twitter" and "chirp," all of them echoing the sound itself. It surfaced as bird-talk in the 19th century. The internet meaning arrived in the late 2000s, when Twitter borrowed the bird's voice for its short messages — fittingly, since the company's logo was a bird and its posts were imagined as tiny chirps from the crowd.