When something is really, really good. Like, better than just 'good' - it's amazing!
That concert was fantastic!
I had a fantastic time on vacation.
She did a fantastic job on the presentation.
Something that's based on imagination and not real life. It's like something out of a fairy tale or a fantasy novel.
The movie had fantastic creatures and magical spells.
He told a fantastic story about finding a pot of gold.
Her drawings were full of fantastic landscapes.
When something is so weird or strange that it's almost unbelievable or comical.
He wore a fantastic outfit to the party.
The building had a fantastic design with strange angles and shapes.
The plot of the movie was so fantastic it was hard to follow.
An idea that is unrealistic or foolish.
His fantastic idea of becoming a millionaire overnight was quickly dismissed.
She had a fantastic notion of traveling the world without any money.