kryptonite

American  

[krip-tuh-nahyt] / ˈkrɪp təˌnaɪt /

noun

1. Usually Kryptonite a fictional radioactive substance that is the only thing capable of hurting or weakening the otherwise invulnerable superhero Superman.

   Exposure to Kryptonite nullifies Superman's powers and immobilizes him with pain.

2. Sometimes Kryptonite something that a person or thing cannot defend against or defeat; a nemesis or bête noire.

   The team has not found a way to stop the triple option attack, which has been their kryptonite over the last several years.

   Garlic oil is kryptonite for aphids.

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Etymology

Origin of kryptonite

Coined in 1943 by writer and producer George Lowther (1913–1975); krypton ( def. ) + -ite ¹ ( def. )