The Collaborative International Dictionary of English v.0.48:

Canter \Can"ter\ (k[a^]n"t[~e]r), v. i. [imp. & p. p. Cantered
   (k[a^]n"t[~e]rd); p. pr. & vb. n. Cantering.]
   To move in a canter.
   [1913 Webster]