Nome do evento no final de Avengers: Infinity War

É chamado a dizimação.

Marvel has been carefully avoiding exploring the consequences of the snap, so as not to spoil any plot details for Avengers 4. With the sole exception of one of the post-credits scenes of Ant-Man & the Wasp, none of the movies have been set in this period. The Marvel Television shows have dodged the snap - even Agents of S.H.I.E.L.D., whose fifth season was heavily influenced by Thanos' attack. This silence has come to an end, however with the publication of Brandon T. Snider's The Cosmic Quest Volume Two: Aftermath. A young adult book, it doesn't go into great detail about the horror of it all, settling for throwaway references to the chaos that ensued on a global scale. But, for the first time, it officially reveals the in-universe name for the event fans have long been calling the "Snappening."

To the Earth's surviving population, the moment when half the life on the planet crumbled to dust is known as "The Decimation."

_{Marvel Reveals Official Name For Thanos' Snap, Thomas Bacon for Screenrant, December 5th, 2018}

Não acredito que o "evento" seja mencionado especificamente pelo nome, mas eu sugiro que provavelmente seja chamado "O desaparecimento".

Evidências circunstanciais fornecidas pelo memorial em São Francisco visitado por Scott Lang.

As pessoas perdidas são chamadas de "Os Desaparecidos".

Como alternativa, parece conhecimento geral que Thanos foi responsável pelo que aconteceu e, portanto, poderia ser referido a um "Antes de Thanos" e "Depois de Thanos"