The Collaborative International Dictionary of English v.0.48:

Spellbind \Spell"bind`\, v. t. [imp. & p. p. Spellbound; p.
   pr. & vb. n. Spellbinding.]
   To bind or hold by, or as if by, a spell or charm; to
   entrance or fascinate, esp. by eloquence of speech, as in a
   political campaign. -- Spell"bind`er, n.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

spellbinder
    n 1: an orator who can hold his listeners spellbound

Moby Thesaurus II by Grady Ward, 1.0:

24 Moby Thesaurus words for "spellbinder":
   Cicero, Circe, Demosthenes, Euryale, Gorgon, Medea, Medusa, Stheno,
   William Jennings Bryan, Winston Churchill, bewitcher, charmer,
   enchanter, enchantress, orator, platform orator, public speaker,
   rhetor, rhetorician, siren, soapbox orator, soapboxer,
   stump orator, vampire