The definition of irritable is someone who is cranky, or who has the tendency to be grumpy and get mad easily.(adjective)
A woman who is very pregnant, has raging hormones and gets really mad at everything all the time is an example of someone who would be described as irritable.
See irritable in Webster's New World College Dictionary
Origin: L irritabilis < irritare, to irritate
See irritable in American Heritage Dictionary 4
Origin: French irritable
Origin: , from Latin irrītābilis
Origin: , from irrītāre, to irritate.
Learn more about irritable