DaseinPronunciation: /ˈdɑːzʌɪn/Definition of Dasein noun [mass noun] Philosophy (in Hegelianism) existence or determinate being; (in existentialism) human existence. Origin: mid 19th century: German, from dasein 'exist', from da 'there' + sein 'be'Dasein in other Oxford dictionaries Definition of Dasein in the US English dictionary