Definition of Grind. 1. v. t. To reduce to powder by friction, as in a mill, or with the teeth; to crush into small fragments; to produce as by the action of millstones. 2. v. i. To perform the operation of grinding something; to turn the millstones. 3. n. The act of reducing to powder, or of sharpening, by friction. Definition of Grind. 1. Verb.