Source : Webster's Revised Unabridged Dictionary (1913)

Oligoclase \Ol"i*go*clase\, n. [Oligo- + Gr. ? fracture, fr. ?
   to break.] (Min.)
   A triclinic soda-lime feldspar. See {Feldspar}.

Source : WordNet®

oligoclase
     n : any of a rock-forming series of triclinic feldspars [syn: {plagioclase}]