The Collaborative International Dictionary of English v.0.48:

Hypericum \Hy*per"i*cum\, n. [L., fr. Gr. ?, ?; ? under, among +
   ?, ?, heath, heather.] (Bot.)
   A genus of plants, generally with dotted leaves and yellow
   flowers; -- called also St. John's-wort.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Hypericum
    n 1: large almost cosmopolitan genus of evergreen or deciduous
         shrubs and herbs with often showy yellow flowers;
         cosmopolitan except tropical lowlands and Arctic or high
         altitudes and desert regions [syn: Hypericum, genus
         Hypericum]