Power, government, war, law, punishment, and a thousand other things, had no terms wherein that language could express them, which made the difficulty almost insuperable, to give my master any conception of what I meant.
There are no more uses of "insuperable" in the book.
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This objection would be insuperable if Homer had been an Ithakan.
Homer -- The Odyssey
I came to the conclusion that difficulties, well-nigh insuperable, lay between me and the safe possession of the beautiful little vessel.