In a deeply established, firmly rooted, or thoroughly engrained manner.
From 'engrained' plus the adverbial suffix '-ly.' A rare formation used to describe actions or qualities that are performed or exist in a deeply embedded way.
This is a rarely used but logically constructed adverb—it's the kind of word that feels natural once you understand it, like saying someone acts 'engrainedly' prejudiced, meaning their prejudice runs impossibly deep.
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