A means of keeping a baseball game going in the event that each team is so small (3 players or so) that a player who is already on base must go back up to bat. An invisible man is then placed on the base previously occupied by the person who has gone up to bat.
See Indian Baseball.
The bases are loaded, and we only have three people on each team. Let's have Tommy go back up to bat, and we'll put an invisible man on third.
When a guy is doing a girl from behind and switches with his buddy mid-course; goes outside (preferably by a window) and waves to his unknowing girlfriend from outside.
Hey man I just gave Cindy the Invisible man. She flipped shit