The Collaborative International Dictionary of English v.0.48:

Tacky \Tack"y\, a. [Cf. Techy, Tack a spot.]
   Sticky; somewhat adhesive;; -- said of paint, varnish, etc.,
   when not well dried. [U. S.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Tacky \Tack"y\, a. [Etymol. uncert.]
   1. Dowdy, shabby, or neglected in appearance; unkempt.
      [Local, U. S.]
      [Webster 1913 Suppl.]

   2. In poor taste; appearing cheap; gaudy; unstylish. Broadly
      used to describe objects whose style is disapproved of by
      the speaker.
      [PJC]

   3. Tactless; in poor taste; -- used to describe behavior.
      [PJC]

The Collaborative International Dictionary of English v.0.48:

Tacky \Tack"y\, n. [Written also tackey.]
   An ill-conditioned, ill-fed, or neglected horse; also, a
   person in a like condition. [Southern U. S.]
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

tacky
    adj 1: (of a glutinous liquid such as paint) not completely
           dried and slightly sticky to the touch; "tacky varnish"
    2: tastelessly showy; "a flash car"; "a flashy ring"; "garish
       colors"; "a gaudy costume"; "loud sport shirts"; "a
       meretricious yet stylish book"; "tawdry ornaments" [syn:
       brassy, cheap, flash, flashy, garish, gaudy,
       gimcrack, loud, meretricious, tacky, tatty,
       tawdry, trashy]

Moby Thesaurus II by Grady Ward, 1.0:

203 Moby Thesaurus words for "tacky":
   Mickey Mouse, adherent, adhesive, amylaceous, base, beat-up,
   bedraggled, blowsy, blowzy, boggy, breakable, brittle, broken-down,
   brummagem, bulldogged, bulldoggish, bulldoggy, bullheaded,
   careless, cheap, cheap-jack, cheesy, chintzy, clabbered, clammy,
   clingy, clotted, coagulated, coarse, cobwebby, common, crude,
   crumbly, curdled, dainty, damp, dampish, dank, delicate,
   delicately weak, dewy, dilapidated, dingy, doughy, dowdy,
   down-at-heel, down-at-the-heels, drabbletailed, draggled,
   draggletailed, effeminate, faded, fenny, flimsy, fourth-class,
   fragile, frail, frangible, frayed, frazzled, frowzy, frumpish,
   frumpy, full of holes, gaudy, gaumy, gelatinous, gimcrack,
   gimcracky, glairy, gluelike, gluey, glutenous, glutinose,
   glutinous, gone to seed, gooey, gossamery, grubby, grumous, gumbo,
   gumbolike, gumlike, gummous, gummy, heavy, holey, humid, in rags,
   in shreds, in tatters, incorrect, inelegant, inferior, informal,
   inspissated, irregular, jelled, jellied, jellylike, jerry,
   jerry-built, light, lightweight, loose, low-class, low-grade,
   low-quality, low-test, lumpen, marshy, mean, messy, moist,
   mucilaginous, muggy, mussy, namby-pamby, negligent, obstinate,
   out-of-date, outmoded, paltry, papery, pasteboardy, pasty, patchy,
   persistent, poky, poor, punk, puny, ragged, raggedy, rainy, ratty,
   ropy, roric, roriferous, ruinous, run-down, scraggly, scruffy,
   second-best, second-class, seedy, self-adhesive, shabby, shattery,
   shoddy, sissified, slabby, slack, slatternly, sleazy, slight,
   slimy, slipshod, slithery, sloppy, slovenly, sluttish, sordid,
   squalid, starchy, stickable, sticky, stodgy, stringy, stubborn,
   swampy, syrupy, tasteless, tattered, tatty, tawdry, tenacious,
   thick, thickened, third-class, third-rate, threadbare, tinny, torn,
   tough, tremelloid, tremellose, unbecoming, undried, unkempt,
   unneat, unsightly, unsubstantial, unsuitable, untidy, viscid,
   viscose, viscous, vulgar, wet, wettish, wispy, womanish