<p><strong>Noun</strong></p><ul><li>a person or thing acting or serving in place of another.</li><li>Synonyms: equivalent, replacement, alternative.</li><li>(formerly) a person who, for payment, served in an army or navy in the place of a conscript.</li><li>Grammar: 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."</li></ul><p><strong>Verb</strong></p><ul><li>(used with object) substituted, substituting:<ul><li>to put (a person or thing) in the place of another.</li><li>to take the place of; replace.</li><li>Chemistry: to replace (one or more elements or groups in a compound) by other elements or groups.</li></ul></li><li>(used without object) substituted, substituting:<ul><li>to act as a substitute.</li></ul></li></ul><p><strong>Adjective</strong></p><ul><li>of or relating to a substitute or substitutes.</li><li>composed of substitutes.</li></ul>