The Collaborative International Dictionary of English v.0.48:

Termagant \Ter"ma*gant\, n. [OE. Trivigant, Termagant, Termagant
   (in sense 1), OF. Tervagan; cf. It. Trivigante.]
   1. An imaginary being supposed by the Christians to be a
      Moslem deity or false god. He is represented in the
      ancient moralities, farces, and puppet shows as extremely
      vociferous and tumultous. [Obs.] --Chaucer. "And
      oftentimes by Termagant and Mahound [Mahomet] swore."
      --Spenser.
      [1913 Webster]

            The lesser part on Christ believed well,
            On Termagant the more, and on Mahound. --Fairfax.
      [1913 Webster]

   2. A boisterous, brawling, turbulent person; -- formerly
      applied to both sexes, now only to women.
      [1913 Webster]

            This terrible termagant, this Nero, this Pharaoh.
                                                  --Bale (1543).
      [1913 Webster]

            The slave of an imperious and reckless termagant.
                                                  --Macaulay.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Termagant \Ter"ma*gant\, a.
   Tumultuous; turbulent; boisterous; furious; quarrelsome;
   scolding. -- Ter"ma*gant*ly, adv.
   [1913 Webster]

         A termagant, imperious, prodigal, profligate wench.
                                                  --Arbuthnot.
   [1913 Webster]

WordNet (r) 3.0 (2006):

termagant
    n 1: a scolding nagging bad-tempered woman [syn: shrew,
         termagant]

Moby Thesaurus II by Grady Ward, 1.0:

80 Moby Thesaurus words for "termagant":
   Jezebel, Mafioso, Xanthippe, Young Turk, amazon, battle-ax, beast,
   beldam, berserk, berserker, bitch, bitch-kitty, boisterous, bomber,
   brute, cat, common scold, demon, devil, disorderly, dragon, fiend,
   fire-eater, firebrand, fishwife, fury, goon, gorilla, grimalkin,
   gunsel, hag, hardnose, harpy, hell-raiser, hellcat, hellhag,
   hellhound, hellion, holy terror, hood, hoodlum, hothead, hotspur,
   incendiary, killer, limitable, mad dog, madcap, monster, mugger,
   ogress, rapist, raucous, revolutionary, rowdy, rowdyish,
   rumbustious, savage, scold, she-devil, she-wolf, shrew, siren,
   spitfire, terror, terrorist, tiger, tigress, tough, tough guy,
   tumultuous, ugly customer, unruly, violent, virago, vixen,
   wild beast, wildcat, witch, wolf