The Collaborative International Dictionary of English v.0.48:

Tarantella \Tar`an*tel"la\, n. [It.] (Mus.)
   (a) A rapid and delirious sort of Neapolitan dance in 6-8
       time, which moves in whirling triplets; -- so called from
       a popular notion of its being a remedy against the
       poisonous bite of the tarantula. Some derive its name
       from Taranto in Apulia.
   (b) Music suited to such a dance.
       [1913 Webster]

WordNet (r) 3.0 (2006):

tarantella
    n 1: music composed in six-eight time for dancing the tarantella
    2: a lively whirling Italian dance for two persons [syn:
       tarantella, tarantelle]