The Collaborative International Dictionary of English v.0.48:

Hun \Hun\, n. [L. Hunni, also Chunni, and Chuni; cf. AS. H?nas,
   H?ne, OHG. H?ni, G. Hunnen.]
   One of a warlike nomadic people of Northern Asia who, in the
   5th century, under Atilla, invaded and conquered a great part
   of Europe.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Hun
    n 1: a member of a nomadic people who invaded Europe in the 4th
         century
    2: offensive term for a person of German descent [syn: Kraut,
       Krauthead, Boche, Jerry, Hun]

Moby Thesaurus II by Grady Ward, 1.0:

19 Moby Thesaurus words for "hun":
   annihilator, arsonist, biblioclast, bomber, burner, demolisher,
   destroyer, dynamitard, dynamiter, exterminator, iconoclast,
   idol breaker, idoloclast, nihilist, ruiner, syndicalist, terrorist,
   vandal, wrecker



Moby Thesaurus II by Grady Ward, 1.0:

20 Moby Thesaurus words for "Hun":
   Anzac, Aussie, Boche, Fritz, GI, Heinie, Jerry, Johnny, Kraut,
   Tommy, Tommy Atkins, Yank, askari, digger, doughboy, jock, poilu,
   redcoat, sepoy, swaddy