WordNet (r) 3.0 (2006):

slithery
    adj 1: having a slippery surface or quality ; "slithery mud";
           "slithery eels"

Moby Thesaurus II by Grady Ward, 1.0:

62 Moby Thesaurus words for "slithery":
   adhesive, amylaceous, buttery, clabbered, clammy, clotted,
   coagulated, curdled, doughy, gaumy, gelatinous, glairy, gluelike,
   gluey, glutenous, glutinose, glutinous, gooey, greased, greasy,
   grumous, gumbo, gumbolike, gumlike, gummous, gummy, heavy,
   inspissated, jelled, jellied, jellylike, lubric, lubricated,
   lubricious, mucilaginous, oiled, oily, pasty, ropy, slabby, slick,
   sliddery, slimy, slipper, slippery, slippy, soaped, starchy,
   sticky, stodgy, stringy, syrupy, tacky, tenacious, thick,
   thickened, tough, tremelloid, tremellose, viscid, viscose,
   viscous