(obsolete) morning mass

(medicine) The anatomic and physiological effect that an ectopic mass (such as a tumor, hematoma, or pleural effusion) causes by displacing or pushing against eutopic structures. It may squeeze and thus occlude blood vessels or lymphatic vessels; pinch nerves; disrupt gastrointestinal volume and peristalsis; and so on.

plural of centre of mass

(physics) The mass of an object as measured by its interaction with gravity; it is equal to its inertial mass.

(physics) The mass of an object measured as its resistance to being accelerated by an applied force; it is equal to its gravitational mass.

plural of mass spectrometer

(medicine, historical) A pill of prepared mercury, used as an aperient, etc.

A morula.

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.