Fat tap
To tap a over wieght person's fat with your hand or any other object! And scream or say fat tap. If you don't say it know one knows what you are doing!
Go up to a fat person (when they are or aren't looking) and tap, poke, or slap their fat. after doing so yell Fat tap.
fat girl tap
A friendly (two) tap motion usually on the leg or back. Not in anyway sexual, but friendly and slightly condescending, albeit not overtly so. Done in reassurance or for emphasis.
I guess he wasn't that into me, as we said goodbye he fat girl tapped me.