The Collaborative International Dictionary of English v.0.48:

Optimate \Op"ti*mate\, a. [L. optimas, -atis, adj., optimates,
   n. pl., the adherents of the best men, the aristocrats, fr.
   optimus the best.]
   Of or pertaining to the nobility or aristocracy. [R.] -- n. A
   nobleman or aristocrat; a chief man in a state or city. [R.]
   --Chapman.
   [1913 Webster]