The Collaborative International Dictionary of English v.0.48:

Poleax \Pole"ax`\, Poleaxe \Pole"axe`\, n. [OE. pollax; cf. OD.
   pollexe. See Poll head, and Ax.]
   Anciently, a kind of battle-ax with a long handle; later, an
   ax or hatchet with a short handle, and a head variously
   patterned; -- used by soldiers, and also by sailors in
   boarding a vessel.
   [1913 Webster] poleaxe

The Collaborative International Dictionary of English v.0.48:

poleax \poleax\, poleaxe \poleaxe\v. t.
   1. To fell with or as if with a poleax; -- often used
      figuratively; as, the entire department was poleaxed after
      the takeover.
      [WordNet 1.5 + PJC]

   2. Stunned; astonished;; as, we couldn't speak, poleaxed by
      the sight in fronnt fo us.
      [PJC]

WordNet (r) 3.0 (2006):

poleax
    n 1: an ax used to slaughter cattle; has a hammer opposite the
         blade [syn: poleax, poleaxe]
    2: a battle ax used in the Middle Ages; a long handled ax and a
       pick [syn: poleax, poleaxe]
    v 1: fell with or as if with a poleax [syn: poleax, poleaxe]