Wiktionary
stand in
n. A substitute; a replacement. vb. To substitute for; to replace; (context theater English) to serve as an understudy.
WordNet
stand in
v. be a substitute; "The young teacher had to substitute for the sick colleague"; "The skim milk substitutes for cream--we are on a strict diet" [syn: substitute, sub, fill in]
Usage examples of "stand in".
She would never stand in the way of anything he wanted, of course, but she was deeply uneasy about this decision.