- 镇定自若 [zhèn dìng zì ruò]
- be perfectly calm and collected; be in possession of oneself; with (great) presence of mind; not turn a hair; undismayed; unflappable; with great composure without turning a hair:
remain calm in face of the ferocious enemy 面对凶残的敌人镇定自若
It's not everybody who can keep as cool as a cucumber in an emergency.
He kept as cool as a cucumber as the newspaper reporters shouted questions at him at once.
In spite of all the criticism he received, he kept a stiff upper lip and said nothing.