1. noun Abbreviation for 'portcullis'. To do the PC needs two or more people, and the question "PC?" is often observed, meaning "will you help me with the portcullis please?". Warning: killers love to lure people to the PC this way so as to jump them. See <subject>?.
2. noun Abbreviation for 'program counter'. If the game is hanging, sometimes people will say "the PC is stuck". See timers.
3. noun Abbreviation for 'personal computer'. Usually an IBM PC clone, but it can be used generically for any home micro.
4. noun Abbreviation for 'player character', ie. persona. People who use this will normally call mobiles NPCs.

In all these cases, the term is usually fully capitalised.