belly graze
The belly graze is a gentle brush of the fingertips across a guy's (or girl's) stomach area when walking by, used to send a subtle, unspoken message to all onlookers that this is MY guy (or gal) and he/she is off limits. This simple technique is also effective in sending the message loud and clear as to which person in the room you are interested in, and shuts down the unwanted affection/attention of another.
When entering a room and walking past the object of your affection, just casually run your fingers across their belly and give them a "belly graze."