tool n 1 a an implement, such as a hammer, saw, or spade, that is used by hand b a power-driven instrument; machine tool c (in combination) a toolkit 2 the cutting part of such an instrument 3 a any of the instruments used by a bookbinder to impress a design on a book cover b a design so impressed 4 anything used as a means of performing an operation or achieving an end he used his boss's absence