The Collaborative International Dictionary of English v.0.48:

Serrulate \Ser"rulate\, Serrulated \Ser"ru*la`ted\, a. [L.
   serrula a little saw, dim. of serra a saw.]
   Finely serrate; having very minute teeth.
   [1913 Webster]

WordNet (r) 3.0 (2006):

serrulate
    adj 1: minutely serrated