The Collaborative International Dictionary of English v.0.48:

Skittish \Skit"tish\, a. [See Skit, v. t.]
   1. Easily frightened; timorous; shy; untrustworthy; as, a
      skittish colt. "A restiff, skittish jade." --L'Estrange.
      [1913 Webster]

   2. Wanton; restive; freakish; volatile; changeable; fickle.
      "Skittish Fortune's hall." --Shak.
      [1913 Webster] -- Skit"tish*ly, adv. --
      Skit"tish*ness, n.
      [1913 Webster]

WordNet (r) 3.0 (2006):

skittish
    adj 1: unpredictably excitable (especially of horses) [syn:
           skittish, flighty, spooky, nervous]