The Collaborative International Dictionary of English v.0.48:

Prickly \Prick"ly\, a.
   Full of sharp points or prickles; armed or covered with
   prickles; as, a prickly shrub.
   [1913 Webster]

   Prickly heat (Med.), a noncontagious cutaneous eruption of
      red pimples, attended with intense itching and tingling of
      the parts affected. It is due to inflammation of the sweat
      glands, and is often brought on by overheating the skin in
      hot weather.

   Prickly pear (Bot.), a name given to several plants of the
      cactaceous genus Opuntia, American plants consisting of
      fleshy, leafless, usually flattened, and often prickly
      joints inserted upon each other. The sessile flowers have
      many petals and numerous stamens. The edible fruit is a
      large pear-shaped berry containing many flattish seeds.
      The common species of the Northern Atlantic States is
      Opuntia vulgaris. In the South and West are many others,
      and in tropical America more than a hundred more. Opuntia
      vulgaris, Opuntia Ficus-Indica, and Opuntia Tuna are
      abundantly introduced in the Mediterranean region, and
      Opuntia Dillenii has become common in India.

   Prickly pole (Bot.), a West Indian palm (Bactris
      Plumierana), the slender trunk of which bears many rings
      of long black prickles.

   Prickly withe (Bot.), a West Indian cactaceous plant
      (Cereus triangularis) having prickly, slender, climbing,
      triangular stems.

   Prickly rat (Zool.), any one of several species of South
      American burrowing rodents belonging to Ctenomys and
      allied genera. The hair is usually intermingled with sharp
      spines.
      [1913 Webster]

WordNet (r) 3.0 (2006):

prickly
    adj 1: very irritable; "bristly exchanges between the White
           House and the press"; "he became prickly and spiteful";
           "witty and waspish about his colleagues" [syn: bristly,
           prickly, splenetic, waspish]
    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:

98 Moby Thesaurus words for "prickly":
   acanaceous, acanthoid, aciculate, aculeate, aculeolate, agitable,
   allergic, anaphylactic, annoying, atingle, bad-tempered, barbed,
   bothersome, brambly, briery, bristly, cantankerous, complex,
   complicated, contentious, cranky, crawling, crawly, delicate,
   difficult, edgy, emotional, emotionally unstable, empathetic,
   empathic, eruptive, excitable, explosive, fractious, fretful,
   goosy, hard, high-mettled, high-spirited, high-strung,
   highly emotional, hyperesthetic, hyperpathic, hypersensitive,
   inflammable, intricate, irascible, irritable, itchy, knotty,
   mettlesome, miffy, muricate, nervous, nettlesome, overrefined,
   oversensible, oversensitive, overtender, passible, peevish,
   perturbable, pettish, petulant, pricking, prickling, pricky,
   refined, responsive, sensitive, setaceous, setose, short-tempered,
   skittish, snappish, spiculate, spiky, spinous, spiny, startlish,
   stinging, supersensitive, sympathetic, tactful, temperamental,
   tender, testy, tetchy, thin-skinned, thistly, thorny, ticklish,
   tingling, tingly, touchy, troublesome, volcanic, waspish