The Collaborative International Dictionary of English v.0.48:
Sneakiness \Sneak"i*ness\, n. The quality of being sneaky. [1913 Webster]WordNet (r) 3.0 (2006):
sneakiness n 1: a disposition to be sly and stealthy and to do things surreptitiously [syn: furtiveness, sneakiness, stealthiness]