What are the most interesting bits of D&D/RPG Jargon?

[Raith5]

My favorite is 'rolling up' a character. We still say it even in the context of point buy, set equipment and fixed hp when we start a campaign.

 

[Zardnaar]

Gish
Grognard
THAC0

 

[Greenstone.Walker]

I fought the BBEG and found the McGruffin.

Was the BBEG Hans Gruber?

 

[Volund]

"Hit points" is one of the perplexing bits of jargon in the game that everyone accepts without too much thought about what they actually are. The rules have always struggled to define them. From the original PHB: "A certain amount of these hit points represent the actual amount of physical punishment that can be sustained. The remainder stands... for skill, luck, and/or magical forces." How much of the remainder? Apparently more than half. "...the majority of hit points are symbolic of combat skill, luck (bestowed by supernatural powers), and magical forces." OK, but in the DMG he then says that "hit points are not actually a measure of physical damage, by and large, as far as characters are concerned." I guess his thoughts on hp were "evolving." He never explains why character class and constitution determine the amount of skill, luck and magical forces a character has.

The 5e PHB says hp are a measure of your character's "toughness" but what does that mean? Physical toughness? It has to be more than that because psychic damage is also a thing and having more hp also means you can withstand more psychic damage, too. I think most of us accept hp as an abstract measure of "how much bad stuff can happen to you before you die" and don't worry about it too much.