whacky vs silly

whacky is not a noun while silly is a noun.

Word	Noun	Adjective	Verb	Adverb
whacky	No	Yes	No	No
silly	Yes	Yes	No	No

As adjectives, whacky and silly are synonyms defined as:

Other synonyms of whacky include goofy, wacky, zany.

whacky (noun)	silly (noun)
	a word used for misbehaving children

whacky (adjective)	silly (adjective)
ludicrous, foolish	dazed from or as if from repeated blows
informal or slang terms for mentally irregular	ludicrous, foolish
	lacking seriousness; given to frivolity
	inspiring scornful pity