A quick-tempered person gets angry very easily. A small thing is enough: a late bus, a loud noise, a wrong word. Temper here is the anger-mood, not how hot the weather is. The word describes a pattern, not one bad afternoon — this person lights up fast, often. It is honest and a little blunt, but it is not a swear word; families say it with a sigh. Close cousins are short-tempered and hot-tempered (same idea; hot-tempered can sound a bit stronger). The kind opposite is even-tempered or patient. Getting angry once, when something truly bad happens, does not make you quick-tempered. The “quick” is the easy trigger, not the size of the problem.