non-ens
/ˌnɒnˈɛnz/Now rare
noun
1A thing which has no existence. Compare nonentity. Now chiefly Philosophy.
2 Cambridge Univ. slang. A freshman who has not yet matriculated. In early use also: the condition of not having matriculated. Now historical and rare.
Origin
Early 17th century; earliest use found in John Davies. From post-classical Latin non ens from classical Latin nōn not + ēns.