When performing oral sex on a man, one punches him in the testicles just before orgasm. The surprise pain replaces any pleasant feelings received from the orgasm, or stops it altogether. Can be used as a punishment or as a sexual act.
If two gay males are involved, and it is being used as a punishment, the term then becomes 'Sucker punch, gay revenge'. However, it is performed in the same way as mentioned above.
So my ex was going down on me and just as I was about to cum, she fully Sucker punched me. It hurt.
So Brett was totally going down on Nick and like totally went all Sucker punch gay revenge on him.