No More Room

Lately, I've been seeing the phrase "800-pound [sometimes the weight varies] gorilla in the room."

It's just "800-pound gorilla," meaning "one that is dominating or uncontrollable because of great size or power." Doesn't matter where he is. In fact, that's the point of the original joke:

Q: Where does an 800-pound gorilla sleep?

A: Anywhere he wants.

Don't confuse it with the "elephant in the room," referring to something that's obviously there but no one wants to talk about.