WordNet (r) 3.0 (2006):

knock out
    v 1: eliminate; "knock out a target"
    2: knock unconscious or senseless; "the boxing champion knocked
       out his opponent in a few seconds" [syn: knock cold, knock
       out, kayo]
    3: destroy or break forcefully; "The windows were knocked out"
    4: overwhelm with admiration; "All the guys were knocked out by
       her charm"
    5: empty (as of tobacco) by knocking out; "knocked out a pipe"

Moby Thesaurus II by Grady Ward, 1.0:

261 Moby Thesaurus words for "knock out":
   KO, anesthetize, author, bang, bash, bat, bat out, beat, becharm,
   bedaze, belt, benumb, besot, bewitch, biff, block out, blunt, bonk,
   botch, bugger, bungle, burn out, call off, cancel, captivate,
   carry away, carve, cast, charm, chisel, chloroform, clap, clip,
   clobber, clout, clump, coauthor, coldcock, collaborate, complete,
   compose, cook, crack, create, cut, dash, dash off, deaden, deal,
   deal a blow, debilitate, deck, defeat, deflate, delectate, delete,
   delight, desensitize, disarm, dish, dispose of, do anyhow,
   do by halves, do carelessly, do for, do in, do offhand, do up,
   dope, drop the curtain, drug, dull, editorialize, efform, enchain,
   enchant, end off, enervate, enrapture, enravish, enthrall,
   entrance, etherize, exhaust, expunge, extinguish, fag, fag out,
   fake up, fascinate, fashion, fatigue, fetch, fetch a blow, figure,
   finalize, finish, fix, flag, fold up, forge, form, formalize,
   formulate, found, frame, frazzle, freak out, free-lance, freeze,
   fudge up, gag, get it over, get over with, get through with, ghost,
   ghostwrite, give the quietus, hamstring, handcuff, harass, hew,
   hit, hit a clip, hobble, hog-tie, imparadise, indite, jab, jade,
   jury-rig, kayo, kibosh, kill, knead, knock, knock cold, knock dead,
   knock down, knock off, knock senseless, knock stiff,
   knock together, knock unconscious, knock up, lash up, lay out,
   let have it, lick into shape, manacle, mint, model, mold, muzzle,
   narcotize, novelize, numb, obtund, outwear, overfatigue,
   overstrain, overtire, overweary, palsy, pamphleteer, paralyze,
   paste, patch, patch together, patch up, perfect, plunk, poke,
   polish off, poop, poop out, pound out, prepare, produce, prostrate,
   punch, put paid to, put to sleep, ravish, rough out, roughcast,
   roughhew, scenarize, scrag, sculpt, sculpture, scuttle, send, set,
   settle, shape, shoot down, silence, sink, slam, slap up, slay,
   slog, slug, smack, smite, snap, soak, sock, stamp, strangle,
   strike, strike at, stun, stupefy, swat, swipe, tailor, thermoform,
   thrill, throttle, throw off, throw on paper, throw together, thump,
   thwack, tickle, tickle pink, tire, tire out, tire to death,
   titillate, torpedo, toss off, toss out, toss together, transport,
   trifle with, truss up, tucker, undo, use up, wallop, weaken, wear,
   wear down, wear on, wear out, weary, whack, wham, whomp up, whop,
   wilt, wind, wipe out, work, wow, write, yerk, zap