The Collaborative International Dictionary of English v.0.48:

Hat \Hat\,
   sing. pres. of Hote to be called. Cf. Hatte. [Obs.] "That
   one hat abstinence." --Piers Plowman.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Hat \Hat\ (h[a^]t), n. [AS. h[ae]t, h[ae]tt; akin to Dan. hat,
   Sw. hatt, Icel. hattr a hat, h["o]ttr hood, D. hoed hat, G.
   hut, OHG. huot, and prob. to L. cassis helmet. [root]13. Cf.
   Hood.]
   A covering for the head; esp., one with a crown and brim,
   made of various materials, and worn by men or women for
   protecting the head from the sun or weather, or for ornament.
   [1913 Webster]

   Hat block, a block on which hats are formed or dressed.

   To pass around the hat, to take up a collection of
      voluntary contributions, which are often received in a
      hat. [Colloq.] --Lowell.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Hat \Hat\ (h[aum]t), a.
   Hot. [Obs.] --Chaucer.
   [1913 Webster]

WordNet (r) 3.0 (2006):

hat
    n 1: headdress that protects the head from bad weather; has
         shaped crown and usually a brim [syn: hat, chapeau,
         lid]
    2: an informal term for a person's role; "he took off his
       politician's hat and talked frankly"
    v 1: put on or wear a hat; "He was unsuitably hatted"
    2: furnish with a hat

Moby Thesaurus II by Grady Ward, 1.0:

114 Moby Thesaurus words for "hat":
   Balmoral, Dutch cap, Panama, Panama hat, Salvation Army bonnet,
   Stetson, astrakhan, balaclava helmet, baseball cap, beany,
   bearskin, beaver, beret, boater, bonnet, boot, bowler, brass hat,
   breech, busby, calash, campaign hat, cap, capote, castor, ceil,
   chapeau, chapeau bras, cloak, cloche, coat, cock-and-pinch, coif,
   cork, coverchief, coxcomb, crown, derby, dome, fantail, fez, frock,
   gown, handkerchief, hard hat, headcloth, headdress, headgear,
   headpiece, headtire, headwear, helmet, homburg, hood, jacket,
   jockey cap, kaffiyeh, kelly, kepi, kerchief, leghorn, lid, mantle,
   millinery, mobcap, mortarboard, nightcap, opera hat, overseas cap,
   peaked cap, picture hat, pillbox, pith hat, pith helmet, plug,
   poke, porkpie, puggree, roof, roof in, rumal, sailor, scraper,
   shirt, shoe, shovel hat, silk hat, skullcap, slouch hat, snood,
   sock, sombrero, stocking, stopper, stovepipe, sun hat, sun helmet,
   sunbonnet, sundown, tam, ten-gallon hat, tin hat, tip, top,
   top hat, topee, topper, trilby, turban, tyrolean hat, wide-awake,
   wimple, wind-cutter, yarmulka



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

HAT
       Help Authoring Tool


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

HAT
       Hashed Address Table


The Jargon File (version 4.4.7, 29 Dec 2003):

hat
 n.

    Common (spoken) name for the circumflex (?^?, ASCII 1011110) character. See
    ASCII for other synonyms.


The Free On-line Dictionary of Computing (30 December 2018):

hat

   A common (spoken) name for the circumflex ("^", ASCII 94)
   character.

   See ASCII for other synonyms.

   [Jargon File]


Easton's 1897 Bible Dictionary:

Hat
   Chald. karb'ela, (Dan. 3:21), properly mantle or pallium. The
   Revised Version renders it "tunic."