(idiomatic) Used to tell someone to control their (bad) temper

Habitual moderation in regard to the indulgence of the natural appetites and passions; restrained or moderate indulgence / Moderation, and sometimes abstinence, in respect to using intoxicating liquors.

Moderate; not excessive / Moderate in the indulgence of the natural appetites or passions / Proceeding from temperance. / Living in an environment that is temperate, not extreme.

(obsolete) To render temperate; to moderate

A general tendency or orientation towards a certain type of mood, a volatile state; a habitual way of thinking, behaving or reacting. / State of mind; mood. / A tendency to become angry.

To moderate or control. / To strengthen or toughen a material, especially metal, by heat treatment; anneal.

present participle of temper

The act by which something is tempered.

In a thoughtfully measured or regulated manner, eschewing extremes.

(in combination) Having a specified disposition or temper. / Pertaining to the metallurgical process for finishing metals.