unreliable

Describes a failure of consistency. Whether applied to a person, a machine, or a piece of information, the central feeling is one of anxiety or hesitation because you cannot predict if the subject will perform as expected. When used for people, it carries a strong negative social connotation, implying a lack of integrity or discipline. It differs from 'dishonest' in that an unreliable person might not be lying on purpose; they may simply be disorganized or flaky. When applied to data or objects, it suggests a technical flaw or instability. An 'unreliable source' is one where the truth is suspect, while an 'unreliable car' is one plagued by mechanical failure. It focuses on the outcome (failure) rather than the intent.