The Collaborative International Dictionary of English v.0.48:

Dragnet \Drag"net`\, n. [Cf. AS. dr[ae]gnet.]
   A net to be drawn along the bottom of a body of water, as in
   fishing.
   [1913 Webster]

WordNet (r) 3.0 (2006):

dragnet
    n 1: a system of coordinated measures for apprehending
         (criminals or other individuals); "caught in the police
         dragnet"
    2: a conical fishnet dragged through the water at great depths
       [syn: trawl, dragnet, trawl net]

Moby Thesaurus II by Grady Ward, 1.0:

76 Moby Thesaurus words for "dragnet":
   abduction, apprehension, arrest, arrestation, bait, birdlime, bola,
   capture, catch, catching, cobweb, collaring, coup,
   domiciliary visit, exploration, fishhook, fly, forage,
   forcible seizure, frisk, gill net, grab, grabbing, ground bait,
   hold, hook, house-search, hunt, hunting, jig, kidnapping, lariat,
   lasso, lime, lure, meshes, nabbing, net, noose, perquisition,
   picking up, plug, posse, pound net, power grab, prehension, probe,
   purse seine, quest, ransacking, rummage, running in, search,
   search party, search warrant, search-and-destroy operation,
   searching, seine, seizure, seizure of power, snare, snatch,
   snatching, sniggle, spinner, springe, squid, stalk, stalking,
   still hunt, taking in, taking into custody, toils, trawl,
   turning over, wobbler