What is "plotholes"

Usage examples of "plotholes".

And by this I don’t mean simply that the series take care to eliminate plotholes and to keep Spaceman Steve’s left arm as the one he is missing throughout the course of the story.

But to a set of fans who regularly write angry letters to Star Trek producers concerning the smallest and most insignificant plotholes, Berman’s actions were downright blasphemous.