US standard spelling of centre of mass.

(physics) The energy present in an object because of its mass

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

(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.

(derogatory) The collective group of people who are considered to be uneducated, uninformed, or in some other way unqualified for inclusion in the speaker's elite circles.

plural of mass extinction

(evolutionary theory, geology) A sharp decrease in the total number of species in a relatively short period of time; specifically, a loss of ∼75% of all species on the planet over a geologically interval of less than 3 million years, as a result of a mass extinction event.

(physics, chemistry) The total number of protons and neutrons in an atomic nucleus. Symbol: A

(physics) The increased mass of an object moving at relativistic speed relative to an observer.

(physics) The mass of a body when it is not moving relative to an observer.