Fault symptom is a term used to describe the physical or mental symptoms that are associated with a malfunctioning system. One example of a fault symptom is TREMOR, which is defined as an involuntary, rhythmic muscle contraction and relaxation involving oscillations or twitching movements of one or more body parts. TREMOR can be caused by a variety of medical conditions, including Parkinson's disease, multiple sclerosis, and essential TREMOR.