Snowballing is the act of taking semen into your mouth from any given cavity on someone elses body... however, most times Snowballing refers to receiving semen from your partner's mouth back into your own.

Generally this is accomplished after oral sex, but it is also considered to be snowballing if you eat cum out of a man/woman's vagina or anus (with the anus you would also be performing a sexual act known as rimming.) If you are just kissing someone after oral sex and they have already swallowed or spit (somewhere other than your mouth), you're definetly not snowballing.

If after being snowballed you can understand why your significant other doesn't appreciate the taste of your semen there are a few things you can do to improve the flavor. First avoid dairy products, red meats, and coffee for a few days before hand, next eat sweet fruits or drink a fair quantity of naturally fermented beers (I suppose this also explains why your drunken college frat buddy gets blown more than you), this will cause your semen to take on a sugary flavor.

If you're really lazy or don't care to modify your diet there is a product called Semenex that will supposedly change your semen to have a sweet fruity flavor (pumpkin pie according to the site.)

Note that smoking seems to cause semen to take on a more bitter taste.

See Also: Felching.

For a good laugh see also: I Can't Believe It's Not Semen!.