n. 1 any small burrowing insect-eating mammal of the family Talpidae, esp. Talpa europaea, with dark velvety fur and very small eyes. 2 colloq. a a spy established deep within an organization and usu. dormant for a long period while attaining a position of trust. b a betrayer of confidential information.
[ ME molle, prob. f. MDu. moll(e), mol, MLG mol, mul ]