The Collaborative International Dictionary of English v.0.48:

Dasheen \Dash`een"\ (d[a^]sh`[=e]n"), n.
   1. A tropical aroid (of the genus Caladium, syn.
      Colocasia) having an edible farinaceous root. It is
      related to the taro and to the tanier, but is much
      superior to it in quality and is as easily cooked as the
      potato. It is a staple food plant of the tropics, being
      prepared like potatoes, and has been introduced into the
      Southern United States.
      [Webster 1913 Suppl.]

   2. a herb of the Pacific islands grown throughout the tropics
      for its edible root and in temperate areas as an
      ornamental for its large glossy leaves.

   Syn: taro, taro plant, dalo, Colocasia esculenta.
        [WordNet 1.5]

   3. the edible starchy tuberous root of taro plants.

   Syn: taro, cocoyam, eddo.
        [WordNet 1.5]

   4. a tropical starchy tuberous root.

   Syn: taro, taro root, cocoyam, edda.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

dasheen
    n 1: edible starchy tuberous root of taro plants [syn: taro,
         cocoyam, dasheen, eddo]
    2: herb of the Pacific islands grown throughout the tropics for
       its edible root and in temperate areas as an ornamental for
       its large glossy leaves [syn: taro, taro plant, dalo,
       dasheen, Colocasia esculenta]
    3: tropical starchy tuberous root [syn: taro, taro root,
       cocoyam, dasheen, edda]