The Collaborative International Dictionary of English v.0.48:

Crabby \Crab"by\ (-b[y^]), a.
   Crabbed; difficult, or perplexing. "Persius is crabby,
   because ancient." --Marston.
   [1913 Webster]

WordNet (r) 3.0 (2006):

crabby
    adj 1: annoyed and irritable [syn: crabbed, crabby, cross,
           fussy, grouchy, grumpy, bad-tempered, ill-
           tempered]