not turn a hair

To show no outward emotion when something bad happens or is announced; to maintain a perfectly calm demeanor. I thought he'd be devastated after losing the race, but he didn't turn a hair. You have to give Jane credit. She didn't turn a hair when the customer started shouting in her face. The woman, not turning a hair, paid nearly $30 grand in cash for the diamond-encrusted necklace.

without turning a hair

Without becoming upset, afraid, or emotional; with a perfectly calm demeanor. My father was a tough man. When our family dog came down with rabies, he took him out back and shot him without turning a hair. Claire, without turning a hair, knocked out the two assailants with her bare hands!

turning a hair, not/without

Showing no sign of agitation or distress; quite unruffled and unafraid. This expression comes from horse-racing, where a horse that is extremely sweaty shows it in the roughening of its hair. It was transferred, but only in the negative, to human sangfroid in the late nineteenth century. Still referring to its origin, Richard D. Blackmore wrote (Dariel, 1897), “She never turned a hair—as the sporting people say.”