When someone is performing a blowjob on you, and just as you're about to cum, they put their thumb over the end of your dick. This causes the cum to shoot back into you, usually straight into your spinal column and crippling you for life.
Person A: How did you become disabled?
Guy in wheelchair: I was having sex with a hooker but she did a blowback on me so she could steal my wallet.
Person A: LOL!
Guy in wheelchair: I was having sex with a hooker but she did a blowback on me so she could steal my wallet.
Person A: LOL!
by NickC. September 15, 2010