mole

noun

1.
the molecular weight of a substance expressed in grams; the basic unit of amount of substance adopted under the Systeme International d'Unites
Derived from:
molal molar
2.
a spy who works against enemy espionage
3.
a small congenital pigmented spot on the skin
4.
a protective structure of stone or concrete; extends from shore into the water to prevent a beach from washing away
5.
small velvety-furred burrowing mammal having small eyes and fossorial forefeet