—n. 1. a person or thing acting or serving in place of another.
2. (formerly) a person who, for payment, served in an army or navy in the place of a conscript.
3. Gram.a word that functions as a replacement for any member of a class of words or constructions, as do in He doesn't know but I do.
—v.t. 1. to put (a person or thing) in the place of another.
2. to take the place of; replace.
3. Chem.to replace (one or more elements or groups in a compound) by other elements or groups.
—v.i. to act as a substitute.
—adj. 1. of or pertaining to a substitute or substitutes.
2. composed of substitutes.