gut reaction

idiomatic

(idiomatic) An instantaneous reaction made without thought.

Japanese Meaning

直感的な反応 / 衝動的な反応

My gut reaction was to say no, but after thinking it over I realized it was the right choice.

直感的な反応は断ることだったが、よく考えたらそれが正しい選択だと気づいた。

Sense（1）

(idiomatic) An instantaneous reaction made without thought.

When he saw that lion leaping towards him, his gut reaction was to run.

gut reactions

（ plural ）