lull vs hush up

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

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

As verbs, hush up is a hypernym of lull; that is, hush up is a word with a broader meaning than lull:

Other hypernyms of lull include hush, quieten, shut up, silence, still.

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

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