The crossword solution for the term 'THIS MIGHT KNOCK YOU OUT' is GAS, which is a three-letter word. GAS is a general term used to describe a variety of substances in a gaseous state at normal atmospheric pressure. It can refer to natural GAS, which is a mixture of hydrocarbons found in underground deposits, or to other gases such as carbon dioxide, nitrogen, and oxygen. In addition, GAS can also refer to flammable gases such as propane, butane, and methane, which are used as fuel sources.