Definition of mesocosm in US English:

mesocosm

noun

Ecology
  • An enclosed and essentially self-sufficient (but not necessarily isolated) experimental environment or ecosystem that is on a larger scale than a laboratory microcosm.

Origin

1980s. From meso- + -cosm.

Pronunciation

mesocosm

/ˈmɛsə(ʊ)ˌkɒz(ə)m/