Unperturbed (adjective)

Not having one's calmness or composure disturbed; calm, relaxed, or composed in a difficult or stressful situation.

Origin:

Late 16th century, from un- + perturbed.

Examples:

1. The veteran police officer remained unperturbed even when shots were fired.
2. The seasoned politician remained unperturbed despite the chaos of the rally.
3. The unperturbed businessman gave his speech with confidence and ease.
4. The unperturbed athlete remained focused and calm during the intense game.
5. She remained unperturbed even when the entire audience was booing her.