fantastic vs marvellous

fantastic and marvellous both are adjectives.

Word	Noun	Adjective	Verb	Adverb
fantastic	No	Yes	No	No
marvellous	No	Yes	No	No

As adjectives, fantastic and marvellous are synonyms defined as:

fantastic and marvellous: extraordinarily good or great; used especially as intensifiers

Other synonyms of fantastic include grand, howling, marvelous, phenomenal, rattling, terrific, tremendous, wonderful, wondrous.

fantastic (adjective)	marvellous (adjective)
extraordinarily good or great; used especially as intensifiers	extraordinarily good or great; used especially as intensifiers
extravagantly fanciful in design, construction, appearance	too improbable to admit of belief
ludicrously odd	being or having the character of a miracle
existing in fancy only
fanciful and unrealistic; foolish