1. a large mass of stone forming a hill, cliff, promontory, or the like.
2. Geology. a. mineral matter of variable composition, consolidated or unconsolidated, assembled in masses or considerable quantities in nature, as by the action of heat or water.
b. a particular kind of such matter: igneous rock.
3. stone in the mass: buildings that stand upon rock.
4. a stone of any size.
5. something resembling or suggesting a rock.