The Collaborative International Dictionary of English v.0.48:

Hyades \Hyades\ n. (Greek mythology)
   The seven daughters of Atlas and half-sisters of the
   Pleiades; they nurtured the infant Dionysus and Zeus placed
   them among the stars as a reward.
   [WordNet 1.5] Hyades

The Collaborative International Dictionary of English v.0.48:

Hyades \Hy"a*des\, Hyads \Hy"ads\, n. pl. [L. Hyades, Gr. ?.]
   (Astron.)
   A cluster of five stars in the face of the constellation
   Taurus, supposed by the ancients to indicate the coming of
   rainy weather when they rose with the sun.
   [1913 Webster]

         Thro' scudding drifts the rainy Hyades
         Vext the dim sea.                        --Tennyson.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Hyades
    n 1: (Greek mythology) 7 daughters of Atlas and half-sisters of
         the Pleiades; they nurtured the infant Dionysus and Zeus
         placed them among the stars as a reward