Cliché [of a person] very calm and poised. James did very well in his TV appearances. He stayed cool, calm, and collected.The bad news didn't seem to distress Jane at all. She remained cool, calm, and collected.
Calm and composed, self-possessed. For example, No matter what the board decides, you have to appear cool, calm, and collected in front of the stockholders . This alliterative synonym for cool as a cucumber dates from the late 1800s.