The percentage rate, or minimum rate of return, that is required by a company, in deciding whether to spend money investing in a project. Derived from a calculation of a company's own 'cost of capital' based upon percentage returns demanded by providers of debt and equity to that company itself.
A type of interest rate - that dictates the minimum amount of profit or interest that is needed before monies are committed to a project or investment. If the projected result delivers a percentage which is below your own cost of capital - then there's no point in doing it really.