hush up vs lull

hush up is not a noun while lull is a noun.

Word	Noun	Adjective	Verb	Adverb
hush up	No	No	Yes	No
lull	Yes	No	Yes	No

As verbs, lull is a hyponym of hush up; that is, lull is a word with a more specific, narrower meaning than hush up:

Other hyponyms of hush up include shush, calm down, shout down, gag, muzzle.

hush up (noun)	lull (noun)
	a period of calm weather
	a pause during which things are calm or activities are diminished

hush up (verb)	lull (verb)
cause to be quiet or not talk	become quiet or less intensive
cover up a misdemeanor, fault, or error	make calm or still
	calm by deception