1. noun: A 'know-it-all' who actually does know it all. They have a mind filled with trivia on almost every subject. This term comes from a character on 'Cheers', Cliff Clavin, played by John Ratzenberger.
2. verb: The act of injecting unnecessary, but true, facts into a conversation.
1. noun: "When it comes to knowing random facts, you are such a Clavin."
2. verb: "You don't have to Clavin everything I say."