The Collaborative International Dictionary of English v.0.48:

Hebdomadal \Heb*dom"a*dal\, Hebdomadary \Heb*dom"a*da*ry\, a.
   [L. hebdomadalis, LL. hebdomadarius: cf. F. hebdomadaire.]
   Consisting of seven days, or occurring at intervals of seven
   days; weekly.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Hebdomadary \Heb*dom"a*da*ry\, n. [LL. hebdomadarius: cf. F.
   hebdomadier.] (R. C. Ch.)
   A member of a chapter or convent, whose week it is to
   officiate in the choir, and perform other services, which, on
   extraordinary occasions, are performed by the superiors.
   [1913 Webster]

WordNet (r) 3.0 (2006):

hebdomadary
    adj 1: of or occurring every seven days; "a weekly visit";
           "weekly paper" [syn: weekly, hebdomadal,
           hebdomadary]