A substitute; a replacement.

To substitute for; to replace; (theater) to serve as an understudy. / To make one of a party in a bet or other speculation. / To take a side in a dispute.

(idiomatic, transitive) To replace; to act as a double or substitute for.

A person of similar size and shape to an actor who "stands in" for that actor during the lengthy process of setting up a shot, but who, unlike a double, does not appear in the film. / A substitute.

Third-person singular simple present indicative form of stand on

present participle of stand on

(nautical) To continue following the same course. / To observe a ceremony or tradition; to insist on proper behavior or recognition.

Third-person singular simple present indicative form of stand in for

present participle of stand in for

The act of standing. / A defensive position or effort. / A resolute, unwavering position; firm opinion; action for a purpose in the face of opposition.