Conveys a judgmental tone when referring to something extraordinarily outdated or old-fashioned. His antediluvian views on technology were evident when he refused to use email.
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Beyond Obsolete
Stronger than 'old-fashioned'; implies something is so outdated that it's almost incomprehensible today. Her cell phone is practically antediluvian, it doesn't even have a color screen!
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Hyperbolic Usage
Often used hyperbolically to exaggerate the age or state of obsolescence of an object. My parents still have an antediluvian TV that's as big as a refrigerator.