The Collaborative International Dictionary of English v.0.48:

Spondaic \Spon*da"ic\ (sp[o^]n*d[=a]"[i^]k), Spondaical
\Spon*da"ic*al\ (-[i^]*kal), a. [L. spondaicus, spondiacus, Gr.
   ?: cf. F. sponda["i]que.]
   1. Of or pertaining to a spondee; consisting of spondees.
      [1913 Webster]

   2. Containing spondees in excess; marked by spondees; as, a
      spondaic hexameter, i. e., one which has a spondee instead
      of a dactyl in the fifth foot.
      [1913 Webster]

WordNet (r) 3.0 (2006):

spondaic
    adj 1: of or consisting of spondees; "spondaic hexameter"