In the context of share trading, the market where investors trade shares among themselves, as opposed to the primary market, where an issuer initially issues shares to investors.

In the context of debt securities and other financial instruments, the market where investors buy previously issued securities from other investors, as opposed to the primary market, where investors subscribe for new securities issued by the issuer or obtain them from an intermediary.

In the context of loans, the market where lenders and other investors trade loans already made to borrowers amongst themselves, as opposed to the primary market, where lenders make loans to borrowers.