The Collaborative International Dictionary of English v.0.48:

Ganza \Gan"za\, n. [Sp. gansa, ganso, goose; of Gothic origin.
   See Gannet, Goose.]
   A kind of wild goose, by a flock of which a virtuoso was
   fabled to be carried to the lunar world. [Also gansa.]
   --Johnson.
   [1913 Webster]