In an antediluvial manner; in a way that is extremely ancient, primitive, or hopelessly outdated.
From 'antediluvial' with the adverbial suffix '-ly', converting the adjective to an adverb form.
Tech startups use 'antediluvially' as a joking putdown for legacy systems—when a company's entire operation runs on code from the 1980s, employees might say they're working 'antediluvially,' and it's no laughing matter for maintenance costs.
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