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]

Moby Thesaurus II by Grady Ward, 1.0:

59 Moby Thesaurus words for "snappish":
   abrupt, acerbic, acid, bearish, bitchy, brusque, cankered,
   cantankerous, choleric, churlish, crabbed, crabby, cranky, cross,
   cross-grained, crusty, curt, cussed, disagreeable, dyspeptic,
   excitable, feisty, fractious, fretful, grouchy, gruff,
   hot-tempered, huffish, huffy, ill-humored, ill-tempered, irascible,
   irritable, mean, moody, morose, ornery, peevish, perverse, pettish,
   petulant, prickly, querulous, quick-tempered, sharp, short,
   short-tempered, snappy, spiteful, spleeny, splenetic, surly, tart,
   temperamental, testy, touchy, ugly, ungracious, waspish