In a deceptious manner; in a way that is deceptive or intended to mislead.
From deceptious + -ly (adverb suffix). This rare adverbial form would modify verbs or adjectives to describe deceptive actions or qualities.
This adverb is so obscure it's almost ceremonial—modern English would just say 'deceptively,' but 'deceptiously' shows how many pathways old English offered for making adverbs from adjectives.
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