A Plot Hole is NOT a simple omission of information or unanswered question. These can only be considered a Plot Hole if said omission has no plausible explanation AND is essential information to the overall story's outcome.
Not a Plot Hole: A small unexplained event in the story.
ACTUAL Plot Hole: In Batman Begins a microwave emitter is used to vaporize the water in Gotham to release a psychedelic drug that the water has been laced with. However, the microwaves would in all actuality caused all of the water molecules in every human body to boil and kill everyone very painfully. But this does not happen in the movie.
NOT a Plot Hole: In The Dark Knight Rises, not explaining how Bruce Wayne manages to get back onto the Island of Gotham after it has been cut off from the rest of the world.
Thats a plot hole you can drive a truck through.
2.An unexplained event or inplausible situation in a storyline.
2. "What I never got about that game 'Doom' was why there were chainsaws on Mars. That just screams, 'PLOT HOLE!'"