What is the meaning of Snowbird?

A bird, Junco hyemalis, the dark-eyed junco.

A bird seen primarily in the winter time.

The snow bunting (Plectrophenax nivalis).

A person, usually one who is retired, who travels from a cold climate to a warmer one in the winter; one who overwinters elsewhere.

One who enlists in fall to desert after winter.

A cocaine user.

Source: wiktionary.org