The Collaborative International Dictionary of English v.0.48:
Incognizance \In*cog"ni*zance\, n. Failure to cognize, apprehended, or notice. [1913 Webster] This incognizance may be explained. --Sir W. Hamilton. [1913 Webster]WordNet (r) 3.0 (2006):
incognizance n 1: a lack of knowledge or recognition [ant: awareness, cognisance, cognizance, consciousness, knowingness]