kryptonite

[ krip-tuh-nahyt ]

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.

Word History and Origins

Origin of kryptonite¹

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

Example Sentences

And similar shards of enthusiasm-killing kryptonite are lodged in John Kasich, Mike Pence and Ted Cruz.

From The Daily Beast

Thankfully, neither iteration relies on lazy storylines involving kryptonite or Lex Luthor (at least not yet).

From The Daily Beast

Interestingly, actual man-child Justin Bieber was cover kryptonite.

From The Daily Beast

But for now, it looks like Republicans are surrounded by kryptonite.

From The Daily Beast

Interesting juice choices like a liver detox or kryptonite mix flavors, like carrot and ginger with apple and grapefruit.

From The Daily Beast

If you buy a Kryptonite bike lock and it can be defeated with a Bic pen, you're not getting very good security for your money.

From Project Gutenberg