[1] : The Collaborative International Dictionary of English v.0.48

tansy \tan"sy\, n. oe. tansaye, f. tanaise; cf. it.  sp.
   tanaceto, nl. tanacetum, pg. atanasia, athanasia, gr.
   'aqanasi`a immortality, fr. 'aqa`natos immortal; 'a priv. +
   qa`natos death.
   1. bot. any plant of the composite genus tanacetum. the
      common tansy tanacetum vulgare has finely divided
      leaves, a strong aromatic odor, and a very bitter taste.
      it is used for medicinal and culinary purposes.
      1913 webster

   2. a dish common in the seventeenth century, made of eggs,
      sugar, rose water, cream, and the juice of herbs, baked
      with butter in a shallow dish. obs. --pepys.
      1913 webster

   double tansy bot., a variety of the common tansy with the
      leaves more dissected than usual.

   tansy mustard bot., a plant sisymbrium canescens of
      the mustard family, with tansylike leaves.
      1913 webster
see also:
tanacetum tanacetum vulgare double tansy tansy mustard sisymbrium canescens 

[2] : WordNet (r) 2.0

tansy mustard
     n : north american herb with bitter-tasting pinnate leaves
         resembling those of tansy syn: descurainia pinnata
see also:
descurainia pinnata 

Tansy >> T Words
Tansy, definition of term: Tansy
tansy_pag1.html

Mustard >> M Words
Mustard, definition of term: Mustard
mustard_pag1.html

Mustard Tree >> M Words
Mustard Tree, definition of term: Mustard Tree
mustard+tree_pag1.html

Mustard Plaster >> M Words
Mustard Plaster, definition of term: Mustard Plaster
mustard+plaster_pag1.html

Tansy Leaf Aste >> T Words
Tansy Leaf Aste, definition of term: Tansy Leaf Aste
tansy+leaf+aste_pag1.html