hair trigger
noun
1- a trigger of a firearm set for release at the slightest pressure（枪的）微力扳机, 小扣力扳机。
1.1
- as modifier figurative liable to change suddenly and violently〈喻〉一触即发的, 容易触发的：
a hair-trigger temperament.
一触即发的火爆脾气。