The Collaborative International Dictionary of English v.0.48:

Gummy \Gum"my\, a. [Compar. Gummer (?); superl. Gummirst.]
   Consisting of gum; viscous; adhesive; producing or containing
   gum; covered with gum or a substance resembling gum.
   [1913 Webster]

         Kindles the gummy bark of fir or pine.   --Milton.
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         Then rubs his gummy eyes.                --Dryden.
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   Gummy tumor (Med.), a gumma.
      [1913 Webster]

WordNet (r) 3.0 (2006):

gummy
    adj 1: having the sticky properties of an adhesive [syn:
           gluey, glutinous, gummy, mucilaginous, pasty,
           sticky, viscid, viscous]
    2: covered with adhesive gum [syn: gummed, gummy]

Moby Thesaurus II by Grady Ward, 1.0:

64 Moby Thesaurus words for "gummy":
   adherent, adhesive, amylaceous, bulldogged, bulldoggish, bulldoggy,
   bullheaded, clabbered, clammy, clingy, clotted, coagulated,
   curdled, doughy, gaumy, gelatinous, glairy, gluelike, gluey,
   glutenous, glutinose, glutinous, gooey, grumous, gumbo, gumbolike,
   gumlike, gummous, heavy, inspissated, jelled, jellied, jellylike,
   mucilaginous, obstinate, pasty, persistent, pitchy, resinic,
   resinoid, resinous, resiny, ropy, self-adhesive, slabby, slimy,
   slithery, starchy, stickable, sticky, stodgy, stringy, stubborn,
   syrupy, tacky, tenacious, thick, thickened, tough, tremelloid,
   tremellose, viscid, viscose, viscous