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

marigold \mar"igold\, n. mary + gold. bot.
   a name for several plants with golden yellow blossoms,
   especially the calendula officinalis see calendula, and
   the cultivated species of tagetes.
   1913 webster

   note: there are several yellow-flowered plants of different
         genera bearing this name; as, the african marigold or
         french marigold of the genus tagetes, of which
         several species and many varieties are found in
         gardens. they are mostly strong-smelling herbs from
         south america and mexico: bur marigold, of the genus
         bidens; corn marigold, of the genus chrysanthemum
         chrysanthemum segetum, a pest in the cornfields of
         italy; fig marigold, of the genus
         mesembryanthemum; marsh marigold, of the genus
         caltha caltha palustris, commonly known in
         america as the cowslip. see marsh marigold.
         1913 webster

   marigold window. arch. see rose window, under rose.
      1913 webster
see also:
calendula officinalis calendula tagetes african marigold french marigold bur marigold 
bidens corn marigold chrysanthemum chrysanthemum segetum fig marigold 
mesembryanthemum marsh marigold caltha caltha palustris cowslip 
marsh marigold marigold window rose window rose 

[2] : WordNet (r) 2.0

marigold
     n : any of various tropical american plants of the genus tagetes
         widely cultivated for their showy yellow or orange
         flowers

Marigold >> M Words
Marigold, definition of term: Marigold
marigold_pag1.html