A small parasitic insect; specifically, a louse (Pediculus humanus or a similar parasitic, biting insect), almost always occurring in the plural and designating the third plague upon Egypt described in Exodus. In broader usage, refers to a minute, pernicious pest; in postbiblical Hebrew extended to refer to gnats or other tiny biting insects. Modern Hebrew and later tradition sometimes identify the term with lice in the biological sense, but in ancient usage, may have included various biting vermin of similar type.