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cool; calm; composed; unconcerned; nonchalant; unmoved; indifferent
all right; fine; OK; okay
彼は平気な顔をしているように見えた。
He seems to have an indifferent expression.
そんなことを言われても全然平気だよ。
I'm fine even if you say something like that.
暑さに平気な体質になりたいものだ。
I want to have a constitution that can handle heat.