Source : Webster's Revised Unabridged Dictionary (1913)

Monosyllabic \Mon`o*syl*lab"ic\, a. [Cf. F. monosyllabique.]
   Being a monosyllable, or composed of monosyllables; as, a
   monosyllabic word; a monosyllabic language. --
   {Mon`o*syl*lab"ic*al*ly}, adv.

Source : WordNet®

monosyllabic
     adj : having or characterized by or consisting of one syllable