The chemical element (symbol Kr) with an atomic number of 36. It is a colourless, odourless noble gas that only reacts with fluorine. It is one of the rarest gases in the Earth's atmosphere.

(fiction, DC Comics fictional milieu) A fictional planet, the native world of Superman, named after the element krypton.

plural of krypton

The infusion of a solid with krypton gas

(inorganic chemistry) The material formed by such kryptonation

(inorganic chemistry) To infuse a solid with krypton gas (especially with radioactive krypton-85).

plural of kryptonate

(physics) A radioactive isotope, ⁸⁵₃₆Kr, having thirty-six protons and forty-nine neutrons

(inorganic chemistry) A binary compound of krypton and fluorine

(figuratively) The one weakness of something or someone that is otherwise invulnerable, an Achilles heel.