The Collaborative International Dictionary of English v.0.48:

Besom \Be"som\, v. t. [imp. & p. p. Besomed.]
   To sweep, as with a besom. [Archaic or Poetic] --Cowper.
   [1913 Webster]

         Rolls back all Greece, and besoms wide the plain.
                                                  --Barlow.
   [1913 Webster]