The Collaborative International Dictionary of English v.0.48:

Slicker \Slick"er\, n.
   That which makes smooth or sleek. Specifically:
   (a) A kind of burnisher for leather.
   (b) (Founding) A curved tool for smoothing the surfaces of a
       mold after the withdrawal of the pattern.
       [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Slicker \Slick"er\, n.
   A waterproof coat. [Western U.S.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

slicker
    n 1: a macintosh made from cotton fabric treated with oil and
         pigment to make it waterproof [syn: oilskin, slicker]
    2: a person with good manners and stylish clothing
    3: someone who leads you to believe something that is not true
       [syn: deceiver, cheat, cheater, trickster,
       beguiler, slicker]

Moby Thesaurus II by Grady Ward, 1.0:

50 Moby Thesaurus words for "slicker":
   abradant, abrasive, bunco artist, bunco steerer, burnish,
   cardsharp, cardsharper, carpetbagger, cheat, cheater, city slicker,
   con artist, con man, confidence man, cosmopolitan, cosmopolite,
   crimp, defrauder, diddler, double-dealer, flimflammer, gypper,
   horse coper, horse trader, jackleg, land pirate, land shark,
   land-grabber, lawn-roller, man of experience, man-about-town,
   mortgage shark, mountebank, pettifogger, pitchman, polish, roller,
   shark, sharp, sharper, sharpie, shortchanger, shyster, sleeker,
   smooth, smoother, sophisticate, spieler, swindler, trickster