Irritable is defined as easily annoyed or readily excited to anger. A sample sentence using irritable is "The toddler missed his daily nap and became irritable."

Irritable bowel syndrome is a disorder of the colon that results in abdominal pain, bloating, excess gas, diarrhea and constipation. One may be able to encourage healthy bowel movements by changing their diet and lifestyle.

Irritable is the correct spelling.

The word irritable works. There are quite a few synomyms.

It means to be irritable or contrary; cantankerous.
Crotchety means to be irritable and grumpily.