A person who writes fiction; a novelist or storyteller.
From 'fiction' plus the agent suffix '-ist' (meaning 'one who practices or is concerned with'). This term gained prominence in the 18th-19th centuries as fiction became a recognized literary form.
Calling someone a 'fictionist' rather than a 'novelist' or 'writer' suggests they're specifically interested in making things up and playing with ideas of reality—it has a philosophical edge to it.
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