The meaning of Lemmings

noun

A small, short-tailed, thickset rodent related to the voles, found in the arctic tundra.

Usage examples:

If there are no seals to hunt, they will eat small whales, lemmings, and even geese.

noun

An animal that looks like a large mouse and lives in cold northern areas. lemmings migrate (= move from one place to another) in large groups and are often, but wrongly, thought to jump off cliffs together.