As far as I know, "justification" is not a true literary term. However, for the sake of this post it is. A justification is a swift smoothing over of a plot-hole or other general problem.
You're reading along and thinking "what an idiot, [insert protagonist's name], why didn't he just do [insert reasonable action here]?". Before you know it (assuming it's a well-written novel) a justification will come along. Most of the time justifications come in the form of dialogue. Sometimes, the author seems to be poking fun at the concept, making the narrator believe that he/she had his/her thoughts read. I love those wily author jokes.
Have you ever made up your own literary term?