fantastic vs howling

fantastic is not a noun while howling is a noun.

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

As adjectives, fantastic and howling are synonyms defined as:

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

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

fantastic (noun)	howling (noun)
	a long loud emotional utterance

fantastic (adjective)	howling (adjective)
extraordinarily good or great; used especially as intensifiers	extraordinarily good or great; used especially as intensifiers
extravagantly fanciful in design, construction, appearance
ludicrously odd
existing in fancy only
fanciful and unrealistic; foolish