The Collaborative International Dictionary of English v.0.48:

Enarthrosis \En`ar*thro"sis\, n. [NL., fr. Gr. ?, fr. ? jointed;
   ? in + ? joint.] (Anat.)
   A ball and socket joint, or the kind of articulation
   represented by such a joint. See Articulation.
   [1913 Webster]

WordNet (r) 3.0 (2006):

enarthrosis
    n 1: a freely moving joint in which a sphere on the head of one
         bone fits into a rounded cavity in the other bone [syn:
         ball-and-socket joint, spheroid joint, cotyloid
         joint, enarthrodial joint, enarthrosis, articulatio
         spheroidea]