WordNet (r) 3.0 (2006):

seal off
    v 1: make tight; secure against leakage; "seal the windows"
         [syn: seal, seal off]
    2: impose a blockade on [syn: blockade, seal off]

Moby Thesaurus II by Grady Ward, 1.0:

48 Moby Thesaurus words for "seal off":
   bang, bar, barricade, batten, batten down, bolt, button, button up,
   choke, choke off, clap, close, close up, constrict, contain,
   contract, cordon, cordon off, cover, fasten, fold, fold up,
   isolate, key, latch, lock, lock out, lock up, occlude, padlock,
   plumb, quarantine, rope off, seal, seal up, seclude, secure,
   segregate, separate, shut, shut the door, shut up, slam, snap,
   squeeze shut, strangle, zip up, zipper