Mass/mæs/ Definition 1 of 5Pro Tip 1/3Quantitative Impression Use 'mass' to imply a large, overwhelming quantity of an unstructured collection. A mass of fans surrounded the celebrity. Pro Tip 2/3Abstract Concept 'Mass' can describe quantities that are not physically tangible, like feelings or abstract ideas. There was a mass of confusion during the evacuation. Pro Tip 3/3Emphasizing Excess Emphasize the excessive nature of something by referring to it as a 'mass'. She had a mass of responsibilities overwhelming her.