The Collaborative International Dictionary of English v.0.48:

Cycadaceous \Cyc`a*da"ceous\ (s?k`?-d?"sh?s or s?`k?-), a.
   (Bot.)
   Pertaining to, or resembling, an order of plants like the
   palms, but having exogenous wood. The sago palm is an
   example.
   [1913 Webster]