WordNet (r) 3.0 (2006):

shoot down
    v 1: move quickly and violently; "The car tore down the street";
         "He came charging into my office" [syn: tear, shoot,
         shoot down, charge, buck]
    2: shoot at and force to come down; "the enemy landed several of
       our aircraft" [syn: down, shoot down, land]
    3: thwart the passage of; "kill a motion"; "he shot down the
       student's proposal" [syn: kill, shoot down, defeat,
       vote down, vote out]

Moby Thesaurus II by Grady Ward, 1.0:

92 Moby Thesaurus words for "shoot down":
   KO, blow to pieces, blow up, brain, bring down, burn to death,
   call off, cancel, charge, cock, complete, cook, cut down,
   cut to pieces, deal a deathblow, defeat, delete, detonate,
   discharge, dish, disintegrate, dispose of, do for, do in, drop,
   drop the curtain, eject, end off, expunge, extinguish, fell,
   finalize, finish, fire, fire off, fix, fold up, frag, get it over,
   get over with, get through with, give the quietus, gun, gun down,
   gun for, hit, incinerate, jugulate, kayo, kibosh, kill, knock out,
   lapidate, lay low, let fly, let off, load, pelt, pepper, perfect,
   pick off, pistol, plug, poleax, polish off, pot, potshoot, potshot,
   prime, put paid to, riddle, scrag, scuttle, settle, shoot,
   shoot at, shoot to death, shotgun, silence, sink, snipe,
   stab to death, stone, stone to death, strike, strike dead,
   take a potshot, torpedo, undo, vaporize, wipe out, zap