(physics) The amount of fissile material needed to support a self-sustaining nuclear chain reaction. / (figuratively) The tipping point.

(physics, analytical chemistry) An analytical technique that measures the mass / charge ratio of the ions formed when a molecule or atom is ionized, vaporized and introduced into a vacuum. Mass spectrometry may also involve breaking molecules into fragments - thus enabling its structure to be determined.

Collectively, the communications media, especially television, radio, and newspapers, that reach the mass of the people.

(military) A body of troops held in military reserve by a general for striking a blow on an exposed flank or wherever the enemy reveals a weak spot.

(Christianity) A religious card that states that a Catholic Mass has been said in honour of a dead person, or as a request for special favours such as improved health or success in a worldly endeavour.

A grave containing many corpses.

(geology) the movement downslope of soil and rock in response to gravity

(physics) the difference between the mass of an atom and the sum of the masses of its individual components in the free state; equivalent to the binding energy

(astronomy) A unit, equal to the mass of the sun, used to express the mass of other stars etc. 1 M_☉ = 2 × 10³⁰ kg.

plural of mass grave