Also found in: Wikipedia.
out coldand out like a light
1. Fig. unconscious. I fell and hit my head. I was out cold for about a minute. Tom fainted! He's out like a light!
2. Fig. intoxicated. Four beers and he was out cold. He sat in his chair at the table, out cold.
3. Fig. sound asleep. After a few minutes of tossing and turning, she was out like a light.
Also, out for the count; out like a light. Unconscious; also, asleep. For example, He crashed into the wall and was out cold, or Willie punched him too hard, and he was out for the count or Don't call Jane; she's out like a light by ten every night. The adjective cold refers to the lack of heat in a dead body and has been used to mean "unconscious" since the second half of the 1800s. The first variant comes from boxing, where a fighter who is knocked down must get up before the referee counts to ten or be declared defeated; it dates from about 1930. The last variant alludes to turning out a light and dates from the first half of the 1900s.
1. mod. unconscious. Paul was out cold when we found him.
2. mod. alcohol intoxicated. He sat in his chair at the table, out cold.