cockroach (n) :
1: Small, soft, squishy animal that cannot bite people, cannot scratch people, cannot eat people. It has no stinger, no eight arms with suction cups, no pointy beak, no odorous spray, no noticeable excrement, plenty of culinary uses in some countries, and probable scientific uses in developing a way to shield ourselves from nuclear weapons.
2: Minor character on The Cosby Show.
3: (Popular usage) Ferocious beast worthy of infinite fear.