Irritable ( Informal ) (9)
(Other definitions for ratty that I've seen before include "Irritable (colloq.)" , "Waspish" , "One messing about in a boat" , "Bad-tempered, irritable as a rodent" , "Moley's friend" .)
(Other definitions for crotchety that I've seen before include "Cross" , "Ill-tempered" , "Difficult" , "Irritable" , "Bad-humoured or peevish" .)