The Collaborative International Dictionary of English v.0.48:
Boniness \Bon"i*ness\, n. The condition or quality of being bony. [1913 Webster]WordNet (r) 3.0 (2006):
boniness n 1: extreme leanness (usually caused by starvation or disease) [syn: bonyness, boniness, emaciation, gauntness, maceration]