Definition of mountain beaver in US English:

mountain beaver

noun

  • A burrowing forest-dwelling rodent occurring only in western North America, from British Columbia to California.

    Aplodontia rufa, the only member of the family Aplodontidae

    Also called sewellel
    • ‘This legislation would have allowed the use of traps on moles, gophers and mountain beavers, and provided additional protections for livestock.’
    • ‘A few years ago, after clearing a slope obscured by fallen trees and nettles for use as a rhododendron glen, they discovered mountain beavers.’