untrustworthy
adj. B2 Upper Intermediate US //ənˈtɹəstˌwɝði// UK //ʌntɹˈʌstwɜːði// un·trust·wor·thy
adj. not honest or reliable. You use this to describe someone or something you cannot believe because they might lie or break their promises.
adj. not reliable or honest; likely to be deceptive or dishonest. Often used to describe a person's character or the integrity of a system.
He is an untrustworthy person who always lies.
The old bridge is considered untrustworthy because it has not been maintained for decades and is at risk of collapse.
The witness was dismissed from the trial because his previous testimony was found to be untrustworthy, casting doubt on the entire investigation's credibility.
From un- + trustworthy.