The Collaborative International Dictionary of English v.0.48:

Snappish \Snap"pish\, a.
   1. Apt to snap at persons or things; eager to bite; as, a
      snapping cur.
      [1913 Webster]

   2. Sharp in reply; apt to speak angrily or testily; easily
      provoked; tart; peevish.
      [1913 Webster]

            The taunting address of a snappish misanthrope.
                                                  --Jeffrey.
      [1913 Webster] -- Snap"pish*ly, adv. --
      Snap"pish*ness, n.
      [1913 Webster]

WordNet (r) 3.0 (2006):

snappish
    adj 1: apt to speak irritably; "a snappish tone of voice" [syn:
           snappish, snappy]