Being one of two born at a birth; as, a twin brother or sister.

One of two produced at a birth, especially by an animal that ordinarily brings forth but one at a birth; -- used chiefly in the plural, and applied to the young of beasts as well as to human young.

A sign and constellation of the zodiac; Gemini. See Gemini.

To be born at the same birth.

either of two offspring born at the same time from the same pregnancy

(astrology) a person who is born while the sun in in Gemini

give birth to twins

One of two children produced in the same pregnancy and born during the same birth process. See the entire definition of Twin

For multiple births that involve more than two fetuses, see multiple birth.