Se·wel·lel n.  Zool. A peculiar gregarious burrowing rodent (Haplodon rufus), native of the coast region of the Northwestern United States. It somewhat resembles a muskrat or marmot, but has only a rudimentary tail. Its head is broad, its eyes are small and its fur is brownish above, gray beneath. It constitutes the family Haplodontidae.  Called also boomer, showt'l, and mountain beaver.
 ◄ ►