1.Missing information or a break in the continuity of a storyline.
2.An unexplained event or inplausible situation in a storyline.
1. "I never understood why Wallace give the ring back at the end of the movie. That was a serious plot hole."
2. "What I never got about that game 'Doom' was why there were chainsaws on Mars. That just screams, 'PLOT HOLE!'"