The Collaborative International Dictionary of English v.0.48:

Japonica \Ja*pon"i*ca\, n. [NL., Japanese, fr. Japonia Japan.]
   (Bot.)
   A species of Camellia (Camellia Japonica), a native of
   Japan, bearing beautiful red or white flowers. Many other
   genera have species of the same name.
   [1913 Webster]

WordNet (r) 3.0 (2006):

japonica
    n 1: greenhouse shrub with glossy green leaves and showy
         fragrant rose-like flowers; cultivated in many varieties
         [syn: japonica, Camellia japonica]
    2: deciduous thorny shrub native to Japan having red blossoms
       [syn: japonica, maule's quince, Chaenomeles japonica]