IPA: /fænˈtæstɪkəl/
KK: /fæn'tæstɪkəl/
Describing something that is imaginative, unusual, or related to fantasy, often in a way that is delightful or extraordinary.
The fantastical creatures in the story captured the children's imaginations.
Fantastical → It is formed from "fantasy" (from Greek "phantasia", meaning imagination or appearance) and the suffix "-ical" (meaning relating to or characterized by). The word "fantastical" describes something that is characterized by imagination or is imaginative in nature.
Think of 'fantasy' as relating to imagination, and remember that 'fantastical' means something that is imaginative or dreamlike.