Source : Webster's Revised Unabridged Dictionary (1913)

Monophonic \Mon`o*phon"ic\, a. [Mono- + Gr. ? a voice.] (Mus.)
   Single-voiced; having but one part; as, a monophonic
   composition; -- opposed to {polyphonic}.

Source : WordNet®

monophonic
     adj 1: designating sound transmission or recording or reproduction
            over a single channel [syn: {mono}, {single-channel}]
     2: consisting of a single melodic line [ant: {polyphonic}]