Definitions

1. verb

to form elaborate and often unrealistic mental images, especially of a happy or exciting nature

“She loves to fantasise about her dream holiday destination.”

2. verb (transitive)

to have or entertain elaborate and often unrealistic mental images, especially of a happy or exciting nature, about someone or something

“The children fantasise about their favourite cartoon characters.”

3. verb (intransitive)

to indulge in or give oneself over to vivid mental images, especially of a happy or exciting nature

“He loves to fantasise and let his imagination run wild.”