imperturbableness
1. [ noun ] calm and unruffled self-assurance
Synonyms: coolness phlegm imperturbability
Examples:

"he performed with all the coolness of a veteran"

Related terms: calmness
Similar spelling:   impermeableness
  imperativeness
  improbableness
  imperturbability
  imperial_elephant
  impermeability
  impracticableness