In a manner characterized by fleeing, hiding, or escaping secretly and unlawfully from a place or situation.
From 'abscond' with the past participle '-ed' and adverbial suffix '-ly'. While grammatically sound, this form is rarely used; people typically say 'in absconsion' or simply use 'abscond' as a verb.
English loves making adverbs, so technically 'abscondedly' is legal—but it sounds so awkward that almost nobody uses it, showing how grammar and actual language use can diverge!
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