When a penis gets stuck in a vagina during coital interactions, as if the penis got vacuumed by a Hoover Dirt Devil.

Dropping all forms of communication with someone you can't stand.Usually done without prior warning.
In networking, black holes refer to places in the network where incoming traffic is silently discarded (or "dropped"), without informing the source that the data did not reach its intended recipient so...

When someone, usually after some type of romantic encounter, chooses to look two inches above your head to avoid eye contact as if you are a black hole.

The sick-to-gut feeling you get when your favorite radio station plays soundgarden's blackhole sun song way too much.

A single point of infinite density and mass. Blackholes mass is so great that nothing can escape it's gravitational pull, not even light.
Blackholes are supposedly a reality but there is no way (currently) to prove that they are what they are. Blackholes are created by a star or planet of great mass exploding and then collapsing in on itself creating a gravitational pull that just pulls everything in more eventually ending in a blackhole. Blackholes are often identified by circles of light that orbit them because of the gravity. Blackholes also give off X-Ray and infared signals making them easier to discover.
Blackholes are often theorized as tears in the time-space continuum meaning they can be portals to other points in space or time. Many sci-fi books and movies theorize blackhole possibilities, such as L. Ron Hubbard's "Mission Earth" novels using blackholes as an energy source.

A nickname for someone who is so deep within another man's ass-hole even light cannot escape.

A game commonly played in college and the military where participants try to get their opponent to look directly at their asshole.

Typically, a participant will try to surprise their opponent by hiding somewhere bent over with their ass cheeks spread. When the person walks into the unsuspecting place he/she is overwhelmed by the sight of the orifice.