The Collaborative International Dictionary of English v.0.48:

gunk \gunk\ n.
   any thick gooey and messy substance. [informal]

   Syn: goo, gook, guck, muck, ooze, sludge, slime.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

gunk
    n 1: any thick, viscous matter [syn: sludge, slime, goo,
         goop, gook, guck, gunk, muck, ooze]

Moby Thesaurus II by Grady Ward, 1.0:

75 Moby Thesaurus words for "gunk":
   adherent, adhesive, albumen, barnacle, batter, bonnyclabber,
   bramble, brier, bulldog, burr, butter, cab, cement, clabber,
   cornstarch, cream, curd, decal, decalcomania, dough, egg white,
   gaum, gel, gelatin, glair, glop, glue, gluten, goo, gook, goop,
   gruel, gumbo, jam, jell, jelly, leech, limpet, loblolly, mire,
   molasses, mucilage, muck, mucus, ooze, pap, paste, plaster,
   porridge, prickle, pudding, pulp, puree, putty, remora, rob, scum,
   semifluid, semiliquid, size, slab, slime, slob, slop, slosh,
   sludge, slush, soup, splosh, starch, sticker, sticky mess, syrup,
   thorn, treacle