adjective (a)

• not alert to danger or deception(adj.all)

  Example:
  The shrieks of unwary animals taken by surprise.
  Some thieves prey especially on unwary travelers.
  Seduce the unwary reader into easy acquiescence.
  

  Antonym:
  wary
  

  source: wordnet30
• Not vigilant against danger; not wary or cautious; unguarded; precipitate; heedless; careless.(adjective)

  source: webster1913