The Collaborative International Dictionary of English v.0.48:

Sedum \Se"dum\, n. [NL., fr. L. sedere to sit; so called in
   allusion to the manner in which the plants attach themselves
   to rocks and walls.] (Bot.)
   A genus of plants, mostly perennial, having succulent leaves
   and cymose flowers; orpine; stonecrop. --Gray.
   [1913 Webster]

WordNet (r) 3.0 (2006):

sedum
    n 1: any of various plants of the genus Sedum