Nuclear holocaust, nuclear cataclysm, or nuclear devastation were other names for a nuclear war or the state of a planet thereafter. It often resulted in nuclear winter.
The Talosians were once a technologically-advanced culture but a nuclear holocaust left Talos IV virtually uninhabitable. (TOS: "The Cage")
In 2268, Spock recollected that Captain Ronald Tracey mentioned there was once a considerable civilization on the planet Omega IV. Spock suggested that the only reasonable explanation for its status would be a war, specifically nuclear devastation or a bacteriological holocaust. (TOS: "The Omega Glory")
Kevin and Rishon Uxbridge were the only survivors of a nuclear holocaust on Rana IV. (TNG: "The Survivors")
Humanity experienced a nuclear holocaust following the Third World War between circa 2026 and 2053. Six hundred million (other sources say 37 million) were killed and major cities were destroyed. This led to the post-atomic horror. (TOS: "Bread and Circuses"; TNG: "Encounter at Farpoint"; Star Trek: First Contact; production art seen in ENT: "In a Mirror, Darkly, Part II")