IPA: /ˈfæn.tə.sɪst/
KK: /ˈfæntəsɪst/
A person who imagines or creates stories, ideas, or situations that are not real, often involving fantasy or imagination.
As a fantasist, she often wrote elaborate stories about magical worlds and adventures.
Fantasist → It is formed from "fantasy" (from Greek "phantasia", meaning imagination or appearance) and "-ist" (meaning one who practices or is concerned with). A fantasist is someone who engages in or is characterized by imagination or fanciful ideas.
Think of someone who is deeply involved in their 'imagination' ('fantasy') and is a 'practitioner' ('-ist') of those imaginative ideas.