What is the definition of in Urban Dictionary?

You're asking for the definition of "in" on Urban Dictionary. However, Urban Dictionary is meant for slang and informal definitions, and "in" is a very common, standard English word with many meanings. It's unlikely to have a unique or specific definition on Urban Dictionary.

To get a proper definition, you need to provide more context. For example:

* "In" as a preposition: "The book is in the bag."

* "In" as an adjective: "That's a hot new style, it's in right now."

* "In" as part of a phrase: "Let's get in on this deal."

Please specify the context or phrase where you encountered the word "in" so I can help you find the relevant meaning.