(astronomy) A star that appears as a double due to an optical illusion; in reality, the stars may be far apart from each other.

An existence or life that has two aspects, particularly when one of them is regarded as embarrassing, immoral, or unlawful and thus kept hidden from a person's family, friends, and work colleagues.

Alternative form of double play

A dilemma in which someone receives contradictory instructions and cannot act on either.

(mycology) Describes an annulus with two layers of tissue.

The process of or results of a second tally, for purposes of accuracy and/or safety. / An error in accounting etc. where something is counted more than once.

To perform a double-count, to count twice.

(sports) A pair of games played one after another between the same teams. / A pair of sporting events, one after the other, at a single venue.

A bet of the same value as the initial one, resulting in either a doubling of a loss, or it being cancelled.

To experience double vision, wherein the eyes do not focus on the same point and a single object is therefore perceived as two.