This is where a person hears an argument or idea and is totally shocked by the idea and refuses to even consider it. If you think about it (reason), this is illogical. All the best ideas were totally shocking (but ultimately true) at the outset. Think of Galileo suggesting to people that the earth is not the centre of the universe, but we live in a solar system and the sun is at the centre. It’s a great idea because he based it on empirical observation, the things he saw. The prevailing view he was trying to replace was based on thought, people guessing how the world worked (actually it was based on the supposed word of God, which was linked to peoples identity, and so they wouldn’t allow the idea to be wrong).
The essence of this fallacy, the logic of it, is that, for an idea to be true, it must be easy to imagine. It mustn’t be too far from what you already believe to be true, but there s no logical reason to say this is the case.