WordNet (r) 3.0 (2006):

close in
    v 1: advance or converge on; "The police were closing in on him"
         [syn: close in, draw in]
    2: surround completely; "Darkness enclosed him"; "They closed in
       the porch with a fence" [syn: enclose, close in,
       inclose, shut in]

Moby Thesaurus II by Grady Ward, 1.0:

95 Moby Thesaurus words for "close in":
   accost, advance, approach, appropinquate, approximate,
   bear down on, bear down upon, bear up, beleaguer, beset, besiege,
   blockade, bound, box in, cage, center, centralize, chamber, close,
   close up, close with, come, come closer, come forward, come near,
   come on, come together, come up, compass, concenter, concentralize,
   concentrate, confront, contain, converge, coop, coop in, coop up,
   cordon, cordon off, corral, draw near, draw nigh, encircle,
   enclose, encompass, encounter, enshrine, envelop, fall in with,
   fence, fence in, funnel, gain upon, hedge, hedge in, hem, hem in,
   house in, immure, impound, imprison, incarcerate, include,
   intersect, jail, kennel, leaguer, meet, mew, mew up,
   narrow the gap, near, nip, pen, pen in, pinch, pocket, proximate,
   quarantine, rail in, run together, shrine, shut in, shut up,
   sidle up to, stable, step up, surround, taper, unite, wall in,
   wrap, yard, yard up