howling vs fantastic

howling is a noun but fantastic is not a noun.

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

As adjectives, howling and fantastic are synonyms defined as:

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

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

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

howling (adjective)	fantastic (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