lemming

noun

• a small, short-tailed, thickset rodent related to the voles, found in the Arctic tundra.

  • Lemmus, Dicrostonyx, and other genera, family Muridae: several species, in particular the Norway lemming (L. lemmus), noted for its fluctuating populations and periodic mass migrations, which in popular belief sometimes culminate in the animals jumping off cliffs into the sea
• a person who unthinkingly joins a mass movement, especially a headlong rush to destruction:the flailings of the lemmings on Wall Street