Refers to being attacked by an overwhelming number of players.
ZOMG is an acronym used in the same context as "OMG!", except the Z does not stand for anything. It was original a typo, as when people type "OMG" they press the left shift key down and inadvertantly hit the Z key as well. It is now often intentionally mispelled, not unlike pwn.
An area of the game separated by loading from one point to the next. A lot of bugs and glitches resolve around 'zoning'.