The Collaborative International Dictionary of English v.0.48:

Madia \Ma"di*a\, n. [NL., fr. Sp. madi, fr. Chilian madi, the
   native name.] (Bot.)
   A genus of composite plants, of which one species (Madia
   sativa) is cultivated for the oil yielded from its seeds by
   pressure. This oil is sometimes used instead of olive oil for
   the table.

   Syn: melosa, Chile tarweed, madia oil plant, Madia sativa.
        [1913 Webster]

WordNet (r) 3.0 (2006):

Madia
    n 1: genus of sticky herbs with yellow flowers open in morning
         or evening but closed in bright light [syn: Madia, genus
         Madia]