From Longman Dictionary of Contemporary EnglishInstinetInstinet trademark an electronic network that allows people to buy and sell shares using a computer when a stock exchange is closed. From Longman Business DictionaryInstinetIn‧sti‧net /ˈɪnstɪnet/ noun [uncountable] trademarkFINANCE an electronic network run by Reuters PLC, on which people using a computer that is able to connect to the network can buy and sell shares when a STOCK EXCHANGE is closedThe stock was trading actively on Instinet.