trigger-happy

[ trig-er-hap-ee ]
/ ˈtrɪg ərˌhæp i /

adjective Informal.

ready to fire a gun at the least provocation, regardless of the situation or probable consequences: a trigger-happy hunter.
heedless and foolhardy in matters of great importance and recklessly advocating action that can result in war: Some called him a trigger-happy candidate.
eager to point out the mistakes or shortcomings of others; aggressively or wantonly critical: He's a trigger-happy editor with a nervous blue pencil.

Origin of trigger-happy

First recorded in 1940–45

British Dictionary definitions for trigger happy

trigger-happy

adjective informal

tending to resort to the use of firearms or violence irresponsibly
tending to act rashly or without due consideration

Idioms and Phrases with trigger happy

trigger happy

Inclined to act violently at the slightest provocation, as in They feared that the President was trigger happy and would send in troops at the drop of a hat. This expression alludes to being too eager to fire a gun. [c. 1940]