1. A large body of matter with no definite shape.
2. A large number of people or objects crowded together.
3. The majority of.
4. Assemble or cause to assemble into a single body or mass.
5. Involving or affecting large numbers of people or things.
Plural Noun: Masses.
Verb forms: Mass, Massed, Massed.
When discussing the atom bomb, mass destruction springs to mind.