The Collaborative International Dictionary of English v.0.48:

Crenate \Cre"nate\ (kr[=e]"n[asl]t), Crenated \Cre"na*ted\
   (kr[=e]"n[asl]*t[e^]d), a. [L. crena notch. See Cranny.]
   (Bot.)
   Having the margin cut into rounded teeth notches, or
   scallops.
   [1913 Webster]

WordNet (r) 3.0 (2006):

crenate
    adj 1: having a margin with rounded scallops [syn: crenate,
           crenated, scalloped]