un·re·li·ableAW [unreliabilityunreliable] BrE [ˌʌnrɪˈlaɪəbl] NAmE [ˌʌnrɪˈlaɪəbl] adjective that cannot be trusted or depended on •The trains are notoriously unreliable. •He's totally unreliable as a source of information. Opp: ↑reliable Derived Word: ↑unreliability