Crisis is a term used frequently in the DC Universe to denote any (potentially) cataclysmic event. It was first used during the Silver Age when heroes from Earth-One and Earth-Two met in Justice League of America #21. The word "Crisis" was then used for various Crossovers events, culminating in the epic Crisis on Infinite Earths which redfined the Multiverse in 1985.
Crises[]
Earth-1985
A · I · G · F · Q
Destruction of the
Original Multiverse
Earth-2006
A · I · G · F · Q
Alexander Luthor attempts to reshape the Multiverse
Earth-2008
A · I · G · F · Q
End to the Crisis Anthology
Silver Age
A · I · G · F · Q
Crises in the
Original Multiverse
Earth-1994
A · I · G · F · Q
Extant and Parallax attempt to reshape History
Earth-2004
A · I · G · F · Q
Heroes' Loved Ones
are Threatened
Preludes[]
Infinite Crisis
Earth-2005
A · I · G · F · Q
Prelude to Infinite Crisis
Final Crisis
Earth-2007
A · I · G · F · Q
Prelude to the Final Crisis