The Collaborative International Dictionary of English v.0.48:

Beleaguer \Be*lea"guer\, v. t. [imp. & p. p. Beleaguered; p.
   pr. & vb. n. Beleaguering.] [D. belegeren (akin to G.
   belagern, Sw. bel[aum]gra, Dan. beleire); pref. be- = E. be-
   + leger bed, camp, army, akin to E. lair. See Lair.]
   To surround with an army so as to preclude escape; to
   besiege; to blockade.
   [1913 Webster]

         The wail of famine in beleaguered towns. --Longfellow.
   [1913 Webster]

   Syn: To block up; environ; invest; encompass.
        [1913 Webster]

WordNet (r) 3.0 (2006):

beleaguering
    n 1: the action of an armed force that surrounds a fortified
         place and isolates it while continuing to attack [syn:
         siege, besieging, beleaguering, military blockade]