The Collaborative International Dictionary of English v.0.48:

Matrimonial \Mat`ri*mo"ni*al\, a. [L. matrimonialis: cf. F.
   matrimonial. See Matrimony.]
   Of or pertaining to marriage; derived from marriage;
   connubial; nuptial; hymeneal; as, matrimonial rights or
   duties.
   [1913 Webster]

         If he relied upon that title, he could be but a king at
         courtesy, and have rather a matrimonial than a regal
         power.                                   --Bacon.
   [1913 Webster]

   Syn: Connubial; conjugal; sponsal; spousal; nuptial;
        hymeneal.
        [1913 Webster]

WordNet (r) 3.0 (2006):

matrimonial
    adj 1: of or relating to the state of marriage; "marital
           status"; "marital fidelity"; "married bliss" [syn:
           marital, matrimonial, married]