conspiratorial
adjective /kənˌspɪrəˈtɔːriəl/
  /kənˌspɪrəˈtɔːriəl/
- connected with, or making you think of, a conspiracy (= a secret plan to do something illegal)
- He takes a conspiratoral view of political life.
 
 - (of a person’s behaviour) suggesting that a secret is being shared
- ‘I know you understand,’ he said and gave a conspiratorial wink.
 - Everything he said seemed conspiratorial.
 - Her voice dropped to a conspiratorial whisper.