When one female prevents another female from getting her "sexy on" or prevents her from sexualy advanceing with another.
Can be done by accident but is rarely so.
"Hey, You blocked my cock so now I am cunt blocking you."
When a friend or person prevents a female from hooking up with a potential mate or engaging in sexual activities with that special someone. Usually done on purpose by a male friend or person who is interested in her that will go to extreme lengths to prevent one from hooking up or getting some. Can be done by accident, but usually not likely.
"She cocked blocked me...so I cunt blocked her."