fourth market
noun[S]
STOCK MARKETukusthebuyingandsellingofsharesdirectlybetweenbanks,financialcompanies, etc.ratherthan on astockexchange:
It isimpossibletoestimatethevolumeof fourthmarketactivitybecausetradesare notsubjecttoreportingrequirements.
Compare
primary market
secondary market
third market