marvellous vs improbable

marvellous and improbable both are adjectives.

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

As adjectives, marvellous and improbable are synonyms defined as:

Other synonyms of marvellous include marvelous, tall.

marvellous (adjective)	improbable (adjective)
extraordinarily good or great; used especially as intensifiers	not likely to be true or to occur or to have occurred
too improbable to admit of belief	having a probability too low to inspire belief
being or having the character of a miracle	too improbable to admit of belief