The Collaborative International Dictionary of English v.0.48:

Stun \Stun\, n.
   The condition of being stunned.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Stun \Stun\, v. t. [imp. & p. p. Stunned; p. pr. & vb. n.
   Stunning.] [OE. stonien, stownien; either fr. AS. stunian
   to resound (cf. D. stenen to groan, G. st["o]hnen, Icel.
   stynja, Gr. ?, Skr. stan to thunder, and E. thunder), or from
   the same source as E. astonish. [root]168.]
   1. To make senseless or dizzy by violence; to render
      senseless by a blow, as on the head.
      [1913 Webster]

            One hung a poleax at his saddlebow,
            And one a heavy mace to stun the foe. --Dryden.
      [1913 Webster]

   2. To dull or deaden the sensibility of; to overcome;
      especially, to overpower one's sense of hearing.
      [1913 Webster]

            And stunned him with the music of the spheres.
                                                  --Pope.
      [1913 Webster]

   3. To astonish; to overpower; to bewilder.
      [1913 Webster]

            William was quite stunned at my discourse. --De Foe.
      [1913 Webster]

WordNet (r) 3.0 (2006):

stun
    v 1: make senseless or dizzy by or as if by a blow; "stun fish"
         [syn: stun, stupefy]
    2: hit something or somebody as if with a sandbag [syn:
       sandbag, stun]
    3: overcome as with astonishment or disbelief; "The news stunned
       her" [syn: stun, bedaze, daze]

Moby Thesaurus II by Grady Ward, 1.0:

94 Moby Thesaurus words for "stun":
   KO, amaze, anesthetize, appall, astonish, astound, awake the dead,
   awe, awestrike, bedaze, bedazzle, bemuse, benumb, besot, bewilder,
   blast, blast the ear, blunt, boggle, boom, bowl down, bowl over,
   chloroform, coldcock, confound, crash, crescendo, daze, dazzle,
   deaden, deafen, desensitize, din, discombobulate, dope, drug, dull,
   dumbfound, dumbfounder, electrify, etherize, fill the air,
   flabbergast, freeze, frighten, horrify, jar, jolt, kayo, knock out,
   knock senseless, knock stiff, knock unconscious, lay out,
   narcotize, nonplus, numb, obtund, overcome, overwhelm, palsy,
   paralyze, peal, perplex, petrify, put to sleep, rattle the windows,
   rend the air, rend the ears, resound, ring, rise, rock the sky,
   scare stiff, scare to death, shake, shake up, shock,
   split the eardrums, split the ears, stagger, startle,
   startle the echoes, strike dead, strike dumb, strike terror into,
   strike with wonder, stupefy, surge, surprise, swell, take aback,
   terrify, thunder



V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

STUN
       Simple Traversal of UDP through NAT (SIP, UDP, NAT, VoIP)