(chemistry) The mass of an individual molecule of an element or compound.

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

(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.

(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

A grave containing many corpses.

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

(meteorology) A particular volume of air, especially one having a roughly uniform temperature, pressure and water vapour content.

plural of mass grave