mole1

noun

• 1a small burrowing insectivorous mammal with dark velvety fur, a long muzzle, and very small eyes.

  • Family Talpidae: several genera and species, including the eastern mole (Scalopus aquaticus) of North America

• 2a spy who achieves over a long period an important position within the security defenses of a country.
• someone within an organization who anonymously betrays confidential information.