The Collaborative International Dictionary of English v.0.48:

Loiterer \Loi"ter*er\, n.
   1. One who loiters; an idler.
      [1913 Webster]

   2. An idle vagrant; a tramp. [Obs.] --Bp. Sanderson.
      [1913 Webster]

WordNet (r) 3.0 (2006):

loiterer
    n 1: someone who lingers aimlessly in or about a place [syn:
         loiterer, lingerer]

Moby Thesaurus II by Grady Ward, 1.0:

48 Moby Thesaurus words for "loiterer":
   clock watcher, dallier, dawdle, dawdler, diddler, dillydallier,
   do-nothing, dolittle, doodler, drone, faineant, foot-dragger,
   gentleman of leisure, goldbrick, goldbricker, goof-off, idler,
   laggard, lie-abed, lingerer, loafer, loller, lotus-eater, lounger,
   lubber, mope, moper, plodder, potterer, procrastinator, putterer,
   sleepyhead, slouch, sloucher, slow goer, slow-foot, slowbelly,
   slowpoke, slug, sluggard, snail, stick-in-the-mud, straggler,
   time killer, time waster, tortoise, trifler,
   waiter on Providence