(1):
(n.) Any like assumption made for convenience, as for passing more rapidly over what is not disputed, and arriving at points really at issue.
(2):
(n.) Fictitious literature; comprehensively, all works of imagination; specifically, novels and romances.
(3):
(n.) That which is feigned, invented, or imagined; especially, a feigned or invented story, whether oral or written. Hence: A story told in order to deceive; a fabrication; - opposed to fact, or reality.
(4):
(n.) The act of feigning, inventing, or imagining; as, by a mere fiction of the mind.
(5):
(n.) An assumption of a possible thing as a fact, irrespective of the question of its truth.