A piggyback is a securities offering that combines primary and secondary shares. It is a public offering of securities that is partly a primary seasoned offering and partly a secondary seasoned offering. Before the expiration of the lockup period that prevents corporate management and other insiders from selling their holdings, the issuing company reappears in the market with a new sale of stock that consists of both new shares from the company and existing shares held by the insiders. Previously, insiders- including venture capitalists and other founding investors- would have had to wait at least six months to sell their holdings after an initial public offering (IPO). With the piggybacks (PBOs), insiders can unload a portion of their holdings in as short a period as three months.

It is also termed a combined seasoned offering or a hybrid offering.