1. the class of literature comprising works of imaginative narration, esp. in prose form.
   
2. works of this class, as novels or short stories: detective fiction.
   
3. something feigned, invented, or imagined; a made-up story: We've all heard the fiction of her being in delicate health.
4. the act of feigning, inventing, or imagining.
5. an imaginary thing or event, postulated for the purposes of argument or explanation.
6. Law. an allegation that a fact exists that is known not to exist, made by authority of law to bring a case within the operation of a rule of law.