mole

A massive, usually stone wall constructed in the sea, used as a breakwater and built to enclose or protect an anchorage or a harbor.

The anchorage or harbor enclosed by a mole.

Any of various small insectivorous mammals of the family Talpidae of North America and Eurasia, usually living underground and having a thickset body with light brown to dark gray silky fur, strong forefeet for burrowing, and often rudimentary eyes.

A machine that bores through hard surfaces, used especially for tunneling through rock.

A spy who operates from within an organization, especially a double agent operating against his or her own government from within its intelligence establishment.