forbidding vs ominous

forbidding is a noun but ominous is not a noun.

Word	Noun	Adjective	Verb	Adverb
forbidding	Yes	Yes	No	No
ominous	No	Yes	No	No

As adjectives, forbidding and ominous are synonyms defined as:

forbidding and ominous: threatening or foreshadowing evil or tragic developments

Other synonyms of forbidding include baleful, menacing, minacious, minatory, sinister, threatening.

forbidding (noun)	ominous (noun)
an official prohibition or edict against something

forbidding (adjective)	ominous (adjective)
threatening or foreshadowing evil or tragic developments	threatening or foreshadowing evil or tragic developments
harshly uninviting or formidable in manner or appearance	presaging ill fortune