WordNet sense 1 (the area in which something exists or lives):

environment, environs, surroundings

WordNet sense 2 (be around):

circle, encircle, ring, round, environ

WordNet sense 3 (envelop completely):

smother

WordNet sense 4 (extend on all sides of simultaneously; encircle):

border, skirt

WordNet sense 5 (surround with a wall in order to fortify):

fence, palisade, wall, fence in

WordNet sense 6 (surround so as to force to give up):

beleaguer, besiege, circumvent, hem in