In a way that is extremely bad, shocking, or obviously wrong; blatantly or outrageously.
From 'egregious' (Latin egregiusmeaning 'standing out from the crowd,' from e- 'out of' + gregis 'flock/herd'), formed by adding the adverbial suffix -ly.
Egregious originally meant 'remarkably good' in Latin, but English flipped it to mean 'remarkably bad'—a complete reversal that happened around the 1500s, showing how words can do total personality changes in meaning over centuries.
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