Existing in or constructed from fantasy; of or relating to fantasy; fanciful. / Not believable; implausible; seemingly only possible in fantasy.

(archaic) A fanciful or whimsical person.

Of or pertaining to fantasy. / Fanciful or whimsical. / Fantastic.

In a fantastic manner. / To an extent only in fantasy; outrageously; ridiculously.

(transitive) To make fantastical. / (intransitive) To behave fantastically.

(obsolete) fantasticalness

The quality of being fantastical. / Anything that is fantastical.

plural of fantasticality

(rare) The state of being fantastic.

present participle of fantasticate