In a manner indicating loss or destruction; in a way that shows something has perished or been lost.
From deperdite (lost, ruined) plus -ly (adverbial suffix). This extremely rare adverbial formation suggests an action or state characterized by loss.
'Deperditely' is essentially a ghost word—it's theoretically grammatical but appears so rarely in English that most dictionaries don't list it, making it a perfect example of how language allows infinite word creation even when usage doesn't follow.
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