Having an even temper; calm and collected(adjective)
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Use "coolheaded" in a sentence
"He urged governments and conservationists to be "coolheaded," saying: "Our decisions on these important issues must not be based on emotion but credible scientific data.""
"The postgame analysis in the media, though, was that the coolheaded Obama had won the night, displaying a firm grasp of the facts, while John, they tried to convince voters, had seemed irritable and condescending."
"At that exact moment of terrestrial frenzy, our own Venerable Captain Star Ice, who is known for his coolheaded analysis and time-tested platinum nerves under all conditions of adversity, started to emit a guttural perturbation that soon increased its pitch to a high decibel roar:"