treachery

/ˈtrɛtʃəri/
noun
  1. The act of betraying someone's trust; disloyalty.
    • The novel is full of political treachery and secret alliances.
    • The general was executed for his treachery against the kingdom.
    • She felt a deep sense of treachery when her best friend stole her idea.
  2. The quality of being dangerously unpredictable (less common, usually in plural or literary use).
    • The treacheries of the Arctic weather claimed many explorers.
    • They learned to respect the treachery of the sea after their boat nearly capsized.
    • The map warned of the treacheries hidden in the swamp.