The Collaborative International Dictionary of English v.0.48:

Tradescantia \Trad`es*can"ti*a\, prop. n. (Bot.)
   A genus including spiderwort and Wandering Jew.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Tradescantia
    n 1: spiderworts [syn: Tradescantia, genus Tradescantia]