"Out like a light" is a common expression used to describe someone who has fallen into a deep and peaceful sleep. However, there are many other words and phrases that can be used to convey the same idea. For instance, you could say someone is "sound asleep," "in a deep slumber," or "dead to the world." Other synonyms for "out like a light" include "fast asleep," "comatose," "unconscious," and "in a state of oblivion." So, next time you want to describe the state of someone who is fast asleep, consider using one of these alternative expressions to add a little variety to your vocabulary.