The Collaborative International Dictionary of English v.0.48:

Spiny \Spin"y\, a. [From Spine.]
   1. Full of spines; thorny; as, a spiny tree.
      [1913 Webster]

   2. Like a spine in shape; slender. "Spiny grasshoppers sit
      chirping." --Chapman.
      [1913 Webster]

   3. Fig.: Abounding with difficulties or annoyances.
      [1913 Webster]

            The spiny deserts of scholastic philosophy. --Bp.
                                                  Warburton.
      [1913 Webster]

   Spiny lobster. (Zool.) Same as Rock lobster, under
      Rock. See also Lobster.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Spiny \Spin"y\, n.
   See Spinny.
   [1913 Webster]

WordNet (r) 3.0 (2006):

spiny
    adj 1: having spines; "the dorsal fin is spinous" [syn:
           spinous, spiny] [ant: spineless]
    2: having or covered with protective barbs or quills or spines
       or thorns or setae etc.; "a horse with a short bristly mane";
       "bristly shrubs"; "burred fruits"; "setaceous whiskers" [syn:
       barbed, barbellate, briary, briery, bristled,
       bristly, burred, burry, prickly, setose,
       setaceous, spiny, thorny]

Moby Thesaurus II by Grady Ward, 1.0:

72 Moby Thesaurus words for "spiny":
   Herculean, abstruse, acanthoid, acanthous, acicular, acuate,
   aculeate, aculeiform, acuminate, acute, arduous, barbed, brutal,
   complex, cornuted, critical, cusped, cuspidate, delicate,
   demanding, difficile, difficult, exacting, formidable, hairy, hard,
   hard-earned, hard-fought, hispid, horned, horny, intricate,
   jawbreaking, knotted, knotty, laborious, mean, mucronate,
   needle-pointed, needle-sharp, nettlesome, no picnic, not easy,
   operose, pointed, prickly, pronged, rigorous, rough, rugged,
   set with thorns, severe, sharp-pointed, spiculate, spiked, spiky,
   spined, spinous, steep, strenuous, tapered, tapering, thorny,
   ticklish, tined, toilsome, toothed, tough, tricky, unbated, uphill,
   wicked