The Collaborative International Dictionary of English v.0.48:

Chicken \Chick"en\, n. [AS. cicen, cyceun, dim. of coc cock;
   akin to LG. kiken, k["u]ken, D. Kieken, kuiken, G.
   k["u]chkein. See Cock the animal.]
   1. A young bird or fowl, esp. a young barnyard fowl.
      [1913 Webster]

   2. A young person; a child; esp. a young woman; a maiden;
      same as spring chicken. "Stella is no chicken." --Swift.
      [1913 Webster]

   Chicken cholera, a contagious disease of fowls; -- so
      called because first studied during the prevalence of a
      cholera epidemic in France. It has no resemblance to true
      cholera.
      [1913 Webster]

WordNet (r) 3.0 (2006):

chicken
    adj 1: easily frightened [syn: chicken, chickenhearted,
           lily-livered, white-livered, yellow, yellow-
           bellied]
    n 1: the flesh of a chicken used for food [syn: chicken,
         poulet, volaille]
    2: a domestic fowl bred for flesh or eggs; believed to have been
       developed from the red jungle fowl [syn: chicken, Gallus
       gallus]
    3: a person who lacks confidence, is irresolute and wishy-washy
       [syn: wimp, chicken, crybaby]
    4: a foolhardy competition; a dangerous activity that is
       continued until one competitor becomes afraid and stops