(sports, snowboarding, skiing) Clipping of 900. (900° spin)

A day job, especially at a large company, emphasizing banality. / The workday itself (the period of the day between 9 am and 5 pm). / One who works in a job from 9 am to 5 pm.

(physics) The only stable isotope of beryllium, ⁹₄Be, having four protons and five neutrons

The date of the attack on the Twin Towers and the Pentagon in the USA, September 11th, 2001. / (metonymically) The attack itself.

An event comparable to 9/11.

(climbing) A technical climbing technique used in ice climbing to gain a respite and lessen slack and distance from the undersurface/ceiling which one is climbing underneath, which appears like a number "9" in shape, with one arm anchoring the climber to the surface while hanging upside-down, and one leg wrapped around that arm, forming a figurative "9" in shape.

(psychology) The 1977 revision of the International Classification of Diseases, published by WHO.

plural of 9-to-5

Initialism of carbohydrate antigen 19-9, a tumor marker for colon and pancreatic cancer also found in non-malignant conditions.

Alternative spelling of K9.