Source : Webster's Revised Unabridged Dictionary (1913)

Monoclinic \Mon`o*clin"ic\, a. [Mono- + Gr. ? to incline.]
   (Crystallog.)
   Having one oblique intersection; -- said of that system of
   crystallization in which the vertical axis is inclined to
   one, but at right angles to the other, lateral axis. See
   {Crystallization}.

Source : WordNet®

monoclinic
     adj : having three unequal crystal axes with one oblique
           intersection; "monoclinic system" [ant: {triclinic}]