The Collaborative International Dictionary of English v.0.48:
Invisibleness \In*vis"i*ble*ness\, n. The quality or state of being invisible; invisibility. [1913 Webster]WordNet (r) 3.0 (2006):
invisibleness n 1: the quality of not being perceivable by the eye [syn: invisibility, invisibleness] [ant: visibility, visibleness]