unwary       
adjective uk/ʌnˈweə.ri/ us/ʌnˈwer.i/
 不警惕的,不警觉的;不设防的
not conscious of or careful about possible risks and dangers
  He sold fake insurance policies to unwary customers. 他向未提防的顾客出售假保险。 
 A range of tax and technical issues can trip up the unwary (= unwary people). 一系列的税务和技术问题会使粗心大意的人出错。 
 Synonym: unsuspecting
Opposites: leery suspicious (DOUBT)wary
Compare: gulliblenaive