The Collaborative International Dictionary of English v.0.48:

Arthrodia \Ar*thro"di*a\, n. [NL., fr. Gr. ?, fr. ? well
   articulated; 'a`rqron a joint + ? shape.] (Anat.)
   A form of diarthrodial articulation in which the articular
   surfaces are nearly flat, so that they form only an imperfect
   ball and socket.
   [1913 Webster] Arthrodial