Originally meaning when a person is about to engage in sexual activity and a person (family member, friend, child etc.) stops any chance of doing so. This can also be applied to any day to day non-sexual activity. Such as going out with friends, smoking bud, etc.
"Dude, I was guna get some ass, but then her best friend, who I think is a dyke and totally has a crush on her, cockblocked me."
"Fuck man, we were going to the movies, but then my mom cockblocked me."
The act or reactive measure when the opposite sex makes eye-contact with you and then proceeds to plug in their iPod as a defense mechanism to prevent you from making a move on them.
Josh: I saw this girl on the bus and was going to hit on her, then she busted out her iPod.
A man who dates women with the sole purpose of exploiting their time, energy, and labor while he sucks the joy and happiness from their lives.
"That guy's a soul digger. He'll expect you to work full time, but you'll be doing all the cooking, cleaning, laundry, shopping, and childcare while he plays video games or watches TV."