Rock1  n. 1 a hard material of the earth's crust, often exposed on the surface. B similar material on other planets. 2 geol. Any natural material, hard or soft (e.g. Clay), consisting of one or more minerals. 3 a projecting rock forming a hill, cliff, reef, etc. B (the rock) gibraltar. 4 large detached stone. 5 us stone of any size. 6 firm and dependable support or protection. 7 hard sweet usu. In the form of a peppermint-flavoured stick. 8 slang precious stone, esp. A diamond.  get one's rocks off coarse slang achieve (esp. Sexual) satisfaction. On the rocks colloq. 1 short of money. 2 (of a marriage etc.) Broken down. 3 (of a drink) served neat with ice-cubes. [french roque, roche]