Irascible means very easily made angry. The fuse is short and everybody around knows exactly how short.
It describes a settled temperament rather than a bad afternoon, which is what separates it from irritated. It is a formal and slightly literary word, and it turns up most often describing older men in novels, often affectionately. The related noun is irascibility. Its close relatives are irritable, which is milder and commoner, and choleric, which comes from the old theory of the four humours.
1adjectiveirascibleEasily provoked to anger.
“He was an irascible old man who quarrelled with everyone.”
Latin
īrāscibilis
Old French
irascible
English, today
irascible
From Middle English -, from Old French irascible, from Latin īrāscibilis, from Latin irascor (“to be angry, enraged”) + -bilis. See also -ible.
Etymology from Wiktionary, CC BY-SA