The Collaborative International Dictionary of English v.0.48:

Abarticulation \Ab`ar*tic`u*la"tion\
   ([a^]b`[aum]r*t[i^]k`[-u]*l[=a]"sh[u^]n), n. [L. ab + E.
   articulation : cf. F. abarticulation. See Article.] (Anat.)
   Articulation, usually that kind of articulation which admits
   of free motion in the joint; diarthrosis. --Coxe.
   [1913 Webster]

WordNet (r) 3.0 (2006):

abarticulation
    n 1: dislocation of a joint