mäss

mass adjective [ always before noun ] uk/mæs/ us
involving a lot of people

массовый
mass destruction/unemployment a mass murderer
mass verb [ I,T ]
 formal uk/mæs/ us
to come together somewhere in large numbers, or make people or things do this

собирать(ся) в кучу, скапливаться
Over 20,000 demonstrators mass ed in the town's main square.