The Collaborative International Dictionary of English v.0.48:

Unsuspecting \Unsuspecting\
   See suspecting.

WordNet (r) 3.0 (2006):

unsuspecting
    adj 1: not suspicious; "deceiving the unsuspecting public" [syn:
           unsuspecting, unsuspicious]
    2: (often followed by `of') not knowing or expecting; not
       thinking likely; "an unsuspecting victim"; "unsuspecting (or
       unaware) of the fact that I would one day be their leader"

Moby Thesaurus II by Grady Ward, 1.0:

96 Moby Thesaurus words for "unsuspecting":
   a stranger to, asleep, bare-handed, blind to, caught napping,
   childlike, confiding, credulous, dead to, deaf to, defenseless,
   dependent, depending, doting, easily taken in, easy of belief,
   fond, guardless, guileless, gullible, helpless, ignorant,
   impercipient, in ignorance of, inclined to believe, incognizant,
   inexpectant, infatuated, ingenuous, innocent, insensible,
   insensible to, mindless, naive, napping, nonconceiving,
   nonexpectant, not with it, off guard, out of it, overconfiding,
   overcredulous, overtrustful, overtrusting, reliant, relying,
   superstitious, trustful, trusting, trusty, unadmonished, unadvised,
   unanticipating, unanticipative, unarmed, unarmored, unattended,
   unaware, unaware of, unconscious, unconscious of, uncovered,
   uncritical, undefended, undoubting, unexpecting, unforewarned,
   unfortified, ungarrisoned, unguarded, unguessing, unhearing,
   uninformed, uninsightful, unknowing, unmindful, unmindful of,
   unperceiving, unprehensive, unprepared, unprotected, unready,
   unrealizing, unscreened, unseeing, unsheltered, unshielded,
   unskeptical, unsuspicious, unwarned, unwary, unwatched, unwitting,
   weaponless, without suspicion, witless