Source : Webster's Revised Unabridged Dictionary (1913)

Duet \Du*et"\, n. [{Duetto}.] (Mus.)
   A composition for two performers, whether vocal or
   instrumental.

Source : WordNet®

duet
     n 1: two items of the same kind [syn: {couple}, {pair}, {twosome},
           {twain}, {brace}, {span}, {yoke}, {couplet}, {distich},
           {duo}, {dyad}, {duad}]
     2: two performers or singers who perform together [syn: {duette},
         {duo}]
     3: a pair who associate with one another; "the engaged couple";
        "an inseparable twosome" [syn: {couple}, {twosome}, {duo}]
     4: a musical composition for two performers [syn: {duette}, {duo}]
     5: (ballet) a dance for two people (usually a ballerina and a
        danseur noble) [syn: {pas de deux}]