the act of pulling your testical to the top of your sack, while holding in between your thumb and index finger the loose skin of your scrotum. Then pump your member and slowly release a testical of your choosing out into the loose skin giving the appearance of a tire being pumped up with air.
MUST HAVE A LOOSEY GOOSEY SCROTUM TO PERFORM THE FLAT TIRE. Otherwise injury and embarassment may occur.
My balls are loose, and it's time to pump my flat tire!
Prices shown in USD.