: the quality of seeming real
I first came across the word verisimilitude in Stephen King’s On Writing, a book no aspiring writer should miss out on. I had been of the (ironically) somewhat unrealistic opinion that fiction should mimic reality in every way possible. I am still relentless when it comes to glitches in believability, but I have learned to accept that sometimes, the story is more important.
But what you need to cover up that glitch is not necessarily realism. You need to simulate the reality you are representing in a way that convinces the reader that the setting and the events you describe are plausible.
As a writer you cannot be an expert on every subject, nor can you possibly predict the outcome of events when magic, speculative technology, or alien cultures are involved. But you can make an effort to be as convincing as possible. Aim for plausibility, accept verisimilitude.