a large body of matter with no definite shape

the sun broke out from behind a mass of clouds

a large number of people or objects crowded together

a mass of cyclists

the majority of

the great mass of the population had little interest in the project

the quantity of matter which a body contains, as measured by its acceleration under a given force or by the force exerted on it by a gravitational field

stellar objects of intermediate mass

involving or affecting large numbers of people or things

the film has mass appeal

a mass exodus of refugees

assemble or cause to assemble into a single body or mass

both countries began massing troops in the region

clouds massed heavily on the horizon

the celebration of the Christian Eucharist, especially in the Roman Catholic Church

we went to Mass