The Collaborative International Dictionary of English v.0.48:

Mimosa \Mi*mo"sa\ (?; 277), n. [NL., fr. Gr. ? imitator. Cf.
   Mime.] (Bot.)
   A genus of leguminous plants, containing many species, and
   including the sensitive plants (Mimosa sensitiva, and
   Mimosa pudica).
   [1913 Webster]

   Note: The term mimosa is also applied in commerce to several
         kinds bark imported from Australia, and used in
         tanning; -- called also wattle bark. --Tomlinson.
         [1913 Webster]

WordNet (r) 3.0 (2006):

mimosa
    n 1: evergreen Australasian tree having white or silvery bark
         and young leaves and yellow flowers [syn: silver wattle,
         mimosa, Acacia dealbata]
    2: any of various tropical shrubs or trees of the genus Mimosa
       having usually yellow flowers and compound leaves
    3: a mixed drink containing champagne and orange juice [syn:
       mimosa, buck's fizz]