What does nā̆zismus mean in Latin?

nā̆zismus, a noun, means “Nazism”.

What is the genitive of nā̆zismus?

The genitive singular is nā̆zismī. nā̆zismus is masculine, second declension.

In classical Latin, [naːzˈzɪs.mʊs]; in ecclesiastical (church) Latin, [nadˈd͡ziz.mus].

noun · masculinesecond declension

nā̆zismus m (genitive nā̆zismī)

Classical[naːzˈzɪs.mʊs]Ecclesiastical[nadˈd͡ziz.mus]

Nazism
In particulari pessime deerravit Nazismus, qui tamquam primum fontem et supremam normam totius ordinis moralis et iuridici, posuit, bonum Nationis et instinctum sanguinis.Nazism in particular, which posited the good of the nation and the instinct of blood as the original source and supreme norm of the entire moral and legal order, erred in the worst way.1948, Francesco M. Marchesi, Summula iuris publici ecclesiastici, pages 114–5:
Immo plures Nationes ipso liberalismo democratico valedixerant, et structuram «totalitariam» acceperant: fascismum in Italia, nazismum in Germania, communismum bolscevicum in Russia et alibi.Indeed many nations had bidden farewell to liberal democracy itself, and adopted a “totalitarian” system: fascism in Italy, Nazism in Germany, Bolshevik communism in Russia and elsewhere.1955, Georges Jarlot, “[Introduction to Divini Redemptoris]”, in De Principiis Ethicae Socialis: Documenta Ultimorum Romanorum Pontificum, volume 2, page 60:

Borrowed from German Nazismus. As the first syllable is eventually descended from nātiō, it may be long.