Imperturbable
adj. Unexcitable; unflustered; calm
synomyms
thick-skinned, smug, unmoved
antonyms
touchy, jittery, excitable
sentences
Angela from the office was imperturbable even when she found out she had a day off from work.
The soccer coach was imperturbable even when his team won their last soccer game.
The Office- Season 5- Angela- That's How I Sleep At Night