Double-trigger acceleration is a term that describes the combined sequences of events that lead to a shareholder in a corporation receiving accelerated vesting of that shareholder’s shares. Vesting simply means that the shareholder does not receive the shares right away upon becoming involved with the corporation; instead, the shareholder receives the shares at a later date when certain agreed-upon events may take place. The word trigger is synonymous with event, in the context of the double-trigger acceleration phrase. So, in the case of a double-trigger acceleration scenario, two events must occur, in sequence, in order to trigger the accelerated vesting. An example would be the merger of the corporation with another company followed by a termination of the shareholder’s employment with the corporation. If both of those events were to occur, then the shareholder would take the shareholder’s shares. The remaining details as to how the vesting would occur would typically be set forth in the shareholder’s subscription agreement or some sort of a longer form employment agreement that contains sufficient stock vesting terms. The type of stock that the shareholder receives is usually common stock, since the shareholder will often be taking the stock as an early employee of the company, if not one of the initial founders themselves.