Definition
'Unthought-of' means something that was never even considered or imagined; it existed completely outside the realm of possibility. It is an idea or action that was entirely unforeseen. It is more emphatic than 'unthought' because it suggests a complete absence of consideration. It's like a plot twist in a movie that completely blindsides you. The nuance is that it was so far from being considered that its occurrence feels almost impossible. It is as if it was beyond the horizon of imagination.