Lemming \Lem"ming\ (l[e^]m"m[i^]ng), n. [Nor. lemming, lemende; cf. Sw. lemel, Lapp. lummik.] (Zo["o]l.) Any one of several species of small arctic rodents of the genera {Myodes} and {Cuniculus}, resembling the meadow mice in form. They are found in both hemispheres. Note: The common Northern European lemming ({Myodes lemmus}) is remarkable for making occasional devastating migrations in enormous numbers from the mountains into the lowlands.