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]

The Collaborative International Dictionary of English v.0.48:

Besom \Be"som\, n. [OE. besme, besum, AS. besma; akin to D.
   bezem, OHG pesamo, G. besen; of uncertain origin.]
   A brush of twigs for sweeping; a broom; anything which sweeps
   away or destroys. [Archaic or Fig.]
   [1913 Webster]

         I will sweep it with the besom of destruction. --Isa.
                                                  xiv. 23.
   [1913 Webster]

         The housemaid with her besom.            --W. Irving.
   [1913 Webster]

WordNet (r) 3.0 (2006):

besom
    n 1: a broom made of twigs tied together on a long handle

Easton's 1897 Bible Dictionary:

Besom
   the rendering of a Hebrew word meaning sweeper, occurs only in
   Isa. 14:23, of the sweeping away, the utter ruin, of Babylon.