The Collaborative International Dictionary of English v.0.48:

Chard \Chard\ (ch[aum]rd), n. [Cf. F. carde esculent thistle.]
   1. The tender leaves or leafstalks of the artichoke, white
      beet, etc., blanched for table use.
      [1913 Webster]

   2. A variety of the white beet, which produces large,
      succulent leaves and leafstalks.
      [1913 Webster]

WordNet (r) 3.0 (2006):

chard
    n 1: beet lacking swollen root; grown as a vegetable for its
         edible leaves and stalks [syn: chard, Swiss chard,
         spinach beet, leaf beet, chard plant, Beta vulgaris
         cicla]
    2: long succulent whitish stalks with large green leaves [syn:
       chard, Swiss chard, spinach beet, leaf beet]