WORD - aplomb

aplomb n.
- great composure and coolness under strain
- great self-confidence / self-assuredness
- poise
- assurance of manner or action

sample usage:

Then, unexpectedly, she picked up a microphone and began to sing. She sang several songs, handling herself with the aplomb of a professional entertainer.

--"Rediscovering Japanese Life at a Bike's Pace," New York Times, April 24, 1988