Untrustworthy (adjective)

1. Not dependable or reliable.
2. Not honest or truthful.
3. Not able to be trusted.

Origin:

Middle english, from un- + trustworthy.

Examples:

1. The untrustworthy mechanic was caught overcharging for his services.
2. The untrustworthy employee was fired for embezzlement.
3. The untrustworthy witness's testimony was discredited.
4. The untrustworthy friend broke the confidence and shared the secret.
5. The untrustworthy source was unreliable in providing accurate information.