The shares held by an entity that compose a majority of the outstanding shares of a publicly traded corporation.

The possession of this majority gives the shareholder power to influence the firm's decisions, hence the name 'control stock.' While this usually implies a majority, it doesn't have to. It must merely be a quantity that wins the shareholder the power of influence over the firm. This power is known as a 'controlling interest,' and the company over which it is exerted is known as a 'controlled company.'