As a noun lack
is (obsolete) a defect or failing; moral or spiritual degeneracy.
As a verb lack
is to be without, to need, to require.
As an adjective unsuspecting is
of or pertaining to lack of suspicion
| Related terms
Unsuspecting is a related term of suspicious.
As adjectives the difference between unsuspecting and suspicious
is that unsuspecting
is of or pertaining to lack of suspicion
is arousing suspicion.