I used to play Word Bluff as a kid in a classroom setting, but you can play it with any group of people—again, the more the merrier.
One person looks up a word in the dictionary and writes it on a piece of paper. It has to be a word you don't think anyone in the room has heard before. Everyone then writes down on a piece of paper what they think the word means and puts their name on the paper. All the definitions are then placed into a hat or sack of some kind. You can even just fold the pieces of paper and put them in the middle of the floor. The person who picked the word also puts a definition into the hat—the real definition that is!
Word Bluff is also known as Dictionary in some circles.
All the definitions are read out loud by the person who picked the word and everyone gets to vote for the definition they think is correct.
Each person who guesses correctly scores a point. A point is also given to each person whose wrong definition was believed to be the correct one. If no one guesses the correct definition, the person who originally chose the word gets five points.
The best part about this game is all the crazy false definitions you'll hear. You can make them sound as real or as nutty as you want. But the reader knows the correct definition so he or she will have to read them all out loud with a poker-face.