The Collaborative International Dictionary of English v.0.48:
Chicken-breasted \Chick"en-breast`ed\, a. Having a narrow, projecting chest, caused by forward curvature of the vertebral column. [1913 Webster]WordNet (r) 3.0 (2006):
chicken-breasted adj 1: having a chest deformity marked by a projecting breastbone caused by infantile rickets [syn: pigeon- breasted, chicken-breasted]