Diriment impediment

from WordNet (r) 3.0 (2006)

diriment impediment
    n 1: (canon law) an impediment that invalidates a marriage (such
         as the existence of a prior marriage)

from The Collaborative International Dictionary of English v.0.48

Diriment \Dir"i*ment\, a. [L. dirimens, p. pr. of dirimere. See
   {Dirempt}.] (Law)
   Absolute.
   [1913 Webster]

   {Diriment impediment} (R. C. Ch.), an impediment that
      nullifies marriage.
      [1913 Webster]