The Collaborative International Dictionary of English v.0.48:

Pricker \Prick"er\, n.
   1. One who, or that which, pricks; a pointed instrument; a
      sharp point; a prickle.
      [1913 Webster]

   2. One who spurs forward; a light horseman.
      [1913 Webster]

            The prickers, who rode foremost, . . . halted. --Sir
                                                  W. Scott.
      [1913 Webster]

   3. A priming wire; a priming needle, -- used in blasting and
      gunnery. --Knight.
      [1913 Webster]

   4. (Naut.) A small marline spike having generally a wooden
      handle, -- used in sailmaking. --R. H. Dana, Ir.
      [1913 Webster]

WordNet (r) 3.0 (2006):

pricker
    n 1: a small sharp-pointed tip resembling a spike on a stem or
         leaf [syn: spine, thorn, prickle, pricker,
         sticker, spikelet]
    2: an awl for making small holes for brads or small screws [syn:
       bradawl, pricker]