ツィクロンBMeanings1nounZyklon BHistorical term for the cyanide-based pesticide used in Nazi gas chambers during the Holocaust.ツィクロンBは第だい二に次じ世せ界かい大たい戦せん中ちゅうに毒どくガスとして使し用ようされた。Zyklon B was used as a poison gas during World War II.