- any of various small, mouselike rodents of several genera including Lemmus, Myopus, and Dicrostonyx, of far northern regions, as L. lemmus, of Norway, Sweden, etc., noted for periodic mass migrations that sometimes involve crossing bodies of water. Incidental drownings that have occurred during such passage gave rise to the myth of mass suicides among supposedly frenzied lemmings jumping from cliffs into the sea.
- a person who follows the will of others, especially in a mass movement, and heads straight into a situation or circumstance that is dangerous, stupid, or destructive: These lemmings that eat up conspiracy theories are so blinded by lies, they don’t even see the cliff they’re about to plummet over.
- any of various volelike rodents of the genus Lemmus and related genera, of northern and arctic regions of Europe, Asia, and North America: family Cricetidae. The Scandinavian variety, Lemmus lemmus, migrates periodically when its population reaches a peak
- a member of any large group following an unthinking course towards mass destruction
