Irascible

Irascible \ih-RASS-uh-buhl\ , adjective;
1. Prone to anger; easily provoked to anger; hot-tempered

This word dates to the late 14th century from French irascible, which came from Late Latin irascibilis in the 12th century. The Late Latin word derives from Latin irasci ("grow angry") from ira ("anger"), which comes from the Proto-Indo-European base *eis-, which forms with different words to denote "passion." *Eis- and ira are also the forebears of ire.

Today's word and the first definition were both taken from Dictionary.com's 'Word of the Day' for Tuesday, April 5
Etymologies come from the Oxford English Dictionary and/or Etymonline.com