Source : Webster's Revised Unabridged Dictionary (1913)

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

   {Prickly ash} (Bot.), a prickly shrub ({Xanthoxylum
      Americanum}) with yellowish flowers appearing with the
      leaves. All parts of the plant are pungent and aromatic.
      The southern species is {X. Carolinianum}. --Gray.

   {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. {O.
      vulgaris}, {O. Ficus-Indica}, and {O. Tuna} are abundantly
      introduced in the Mediterranean region, and {O. 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} (Zo["o]l.), any one of several species of South
      American burrowing rodents belonging to {Ctenomys} and
      allied genera. The hair is usually intermingled with sharp
      spines.

Ash \Ash\ ([a^]sh), n. [OE. asch, esh, AS. [ae]sc; akin to OHG.
   asc, Sw. & Dan. ask, Icel. askr, D. esch, G. esche.]
   1. (Bot.) A genus of trees of the Olive family, having
      opposite pinnate leaves, many of the species furnishing
      valuable timber, as the European ash ({Fraxinus
      excelsior}) and the white ash ({F. Americana}).

   {Prickly ash} ({Zanthoxylum Americanum}) and {Poison ash}
      ({Rhus venenata}) are shrubs of different families,
      somewhat resembling the true ashes in their foliage.

   {Mountain ash}. See {Roman tree}, and under {Mountain}.

   2. The tough, elastic wood of the ash tree.

   Note: Ash is used adjectively, or as the first part of a
         compound term; as, ash bud, ash wood, ash tree, etc.

Source : WordNet®

prickly ash
     n 1: any of a number of trees or shrubs of the genus Zanthoxylum
          having spiny branches
     2: Australian tree having alternate simple leaves (when young
        they are pinnate with prickly toothed margins) and slender
        axillary spikes of white flowers [syn: {Orites excelsa}]