The Collaborative International Dictionary of English v.0.48:

Coltish \Colt"ish\, a.
   Like a colt; wanton; frisky.
   [1913 Webster]

         He was all coltish, full of ragery.      --Chaucer.
   -- Colt"ish*ly, adv. -- Colt"ish*ness, n.
   [1913 Webster]