The Collaborative International Dictionary of English v.0.48:

Portulacaceous \Por`tu*la*ca"ceous\, a. (Bot.)
   Of or pertaining to a natural order of plants
   (Portulacace[ae]), of which Portulaca is the type, and
   which includes also the spring beauty (Claytonia) and other
   genera.
   [1913 Webster]