a coherent, typically large body of matter with no definite shape.

a mass of curly hair

a large number of people or objects crowded together.

a mass of cyclists

assemble or cause to assemble into a mass or as one body.

both countries began massing troops in the region

the majority of.

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

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

Every object with mass exerts a gravitational force.