- noun something which is highly amusing or impressive. This sense of the word is inspired by the properties of laughing-gas and is used to denote, e.g., a good joke. This is an Americanism which is also heard in Britain and may have been coined there independently. It was first used before World War II, and is now heard particularly among teenagers.
- noun a depressing experience, person or situation. The word is rare in this sense, in which the image evoked is presumably of a poisonous, asphyxiating or anaesthetic gas.