Source : Webster's Revised Unabridged Dictionary (1913)

Grumpy \Grump"y\, a. [Cf. {Grumble}, and {Grum}.]
   Surly; dissatisfied; grouty. [Collog.] --Ferby.

Source : WordNet®

grumpy
     adj : perversely irritable [syn: {crabbed}, {crabby}, {cross}, {fussy},
            {grouchy}, {bad-tempered}, {ill-tempered}]
     [also: {grumpiest}, {grumpier}]