visible breath; frosty breath
Refers to the misty cloud of breath seen in cold weather. Often used in poetic or descriptive contexts.
On the cold morning, my breath was visible.
He ran while breathing out frosty breath.
Compound of 息 (いき, 'breath') and 白し (しろし, classical form of 白い, 'white'). The exact historical derivation is uncertain, but the word literally describes breath that appears white in cold air.