From 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]
From WordNet (r) 3.0 (2006) :
chickenhearted
adj 1: easily frightened [syn: chicken, chickenhearted,
lily-livered, white-livered, yellow, yellow-
bellied]