Sleep like a log/baby Definition 1 of 2Pro Tip 1/3Deep Uninterrupted Sleep The phrase emphasizes undisturbed sleep with no signs of restlessness, just like a log He slept like a log, not even the thunderstorm woke him up. Pro Tip 2/3Physical Exhaustion Often used after physical exertion, suggesting that the sleep is a result of being very tired. After the marathon, I slept like a log. Pro Tip 3/3Informal Expression This idiom is casual and usually used in informal conversations or writing. Sorry for not answering my phone, I slept like a log last night.