The Collaborative International Dictionary of English v.0.48:

Zygapophysis \Zyg`a*poph"y*sis\, n.; pl. Zygapophyses. [Gr. ?
   a yoke + E. apophysis.] (Anat.)
   One of the articular processes of a vertebra, of which there
   are usually four, two anterior and two posterior. See under
   Vertebra. -- Zyg`ap*o*phys"i*al, a.
   [1913 Webster]