The Collaborative International Dictionary of English v.0.48:

chickenhearted \chickenhearted\, Chicken-hearted
\Chick"en-heart`ed\, a.
   Timid; fearful; cowardly; easily frightened. --Bunyan.
   [1913 Webster]

WordNet (r) 3.0 (2006):

chickenhearted
    adj 1: easily frightened [syn: chicken, chickenhearted,
           lily-livered, white-livered, yellow, yellow-
           bellied]