It is an adjective.
Meaning : irritable.It is an adjective used to indicate a negative quality.It means ill tempered or discontented.
It is derived from Latin word "perversus".
irascible, fractious, fretful, cross, petulant, pettish, crabbed, crabby, crotchety, cantankerous
peevishly - adverb
peevishness - noun
1)Lack of proper sleep tends to make a person dull and peevish.
2)She had become a peevish child without proper guidance.
3)He is a peevish man ,never argue with him.