Definition of ground:

part of speech: verb

To lay or place on the ground; to settle in first principles; to fasten or strike on the bottom, as a ship in too shallow water.

part of speech: noun

The earth or soil, as distinguished from air or water; the surface or upper part of the earth; soil; territory or region; estate or possession; that which supports anything; fundamental cause; primary reason; in a painting, the primary or principal colour; fundamental substance.

part of speech: past tense, past participle

Did grind.