A feeling of doubt or incredulity about the truth or existence of something; an inability or refusal to accept something as true. From dis- (not) + belief. The term 'disbelief' has been used in English since the late 17th century to describe a feeling of doubt or incredulity about the truth or existence of something. It is derived from the prefix 'dis-', meaning 'apart or away', and the verb 'believe', meaning 'to accept something as true or real'.