The definition of composure is the state of being calm and tranquil.
An example of composure is when something upsetting happens but you remain calm and collected instead of becoming overly emotional.
calmness of mind or manner; tranquillity; self-possession
Origin of composurecompos(e) + -ure
A calm or tranquil state of mind; self-possession.
Origin of composureFrom compose.
compose + -ure