mass is on the Basic English 850 List. material - mass - may Pronunciation (UK) IPA (key): /mæs/ or /mɑːs/, SAMPA: /m{s/ (US) IPA (key): /mæs/, SAMPA: /m{s/ Audio (US)(file) Noun Singular mass Plural masses A measure of how much material is in something. Synonyms: ton and bunch The Earth has much more mass than the moon. The spacesuit weighed 75 pounds on Earth but here in outer space it weighed nothing, although its mass was exactly the same. Much material. A mass of dirty branches stopped the river. A Christian ceremony in memory of the Last Supper. Synonym: Eucharist He goes to mass every Sunday. A crowd of people. A mass of protesters gathered at city hall. Wikiwand - on Seamless Wikipedia browsing. On steroids.