prodigious vs portentous

prodigious and portentous both are adjectives.

Word	Noun	Adjective	Verb	Adverb
prodigious	No	Yes	No	No
portentous	No	Yes	No	No

As adjectives, prodigious and portentous are synonyms defined as:

prodigious (adjective)	portentous (adjective)
far beyond what is usual in magnitude or degree	puffed up with vanity
so great in size or force or extent as to elicit awe	ominously prophetic
of momentous or ominous significance	of momentous or ominous significance