WordNet (r) 3.0 (2006):

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

Moby Thesaurus II by Grady Ward, 1.0:

74 Moby Thesaurus words for "goo":
   albumen, bathos, batter, bleeding heart, bonnyclabber, butter, cab,
   clabber, cloyingness, cornstarch, cream, curd, dope, dough,
   egg white, gaum, gel, gelatin, glair, glop, glue, gluten, gook,
   goop, gruel, gumbo, gunk, hearts-and-flowers, jam, jell, jelly,
   loblolly, maudlinness, mawkishness, molasses, mucilage, muck,
   mucus, mush, mushiness, namby-pamby, namby-pambyism,
   namby-pambyness, nostalgia, nostomania, oversentimentalism,
   oversentimentality, pap, paste, porridge, pudding, pulp, puree,
   putty, rob, romanticism, semifluid, semiliquid, sentiment,
   sentimentalism, sentimentality, size, slop, sloppiness, slush,
   soap opera, sob story, soup, starch, sticky mess,
   sweetness and light, syrup, tearjerker, treacle