English to English

adjective (a)

• not expressing or given to expressing the truth(adj.all)

  Example:
  The statement given under oath was untruthful.
  An untruthful person.
  

  Antonym:
  true, truthful
  

  source: wordnet30
• Not truthful; unveracious; contrary to the truth or the fact.(adjective)

  source: webster1913