Describes a personality trait of being easily angered or quick to lose one's temper. Often used in phrases like 癇癖が強い or 癇癖がある.
He has a short temper, so if you don't speak carefully he'll get angry right away.
I'm really troubled by that person's short temper.
Compound of 癇 (かん, 'temper, irritability') and 癖 (へき, 'habit, tendency'). The reading へき becomes ぺき due to rendaku. The exact historical derivation is uncertain, but the word has been used since at least the Edo period to describe a quick-tempered disposition.