out like a light adj. phr.,
informal 1. Fast asleep; to sleep very quickly.
Tom got so much fresh air and exercise that he went out like a light as soon as he lay down.
As soon as the lights were turned off, Johnny was out like a light. 2. In a faint; unconscious.
Johnny was hit by a ball and went out like a light.
After she read that Tom had married another girl Jean was out like a light for several minutes. Compare: OUT COLD.
[TahlilGaran] English Idioms Dictionary ▲