lounge vs mill about

lounge is a noun but mill about is not a noun.

Word	Noun	Adjective	Verb	Adverb
lounge	Yes	No	Yes	No
mill about	No	No	Yes	No

As verbs, lounge and mill about are synonyms defined as:

Other synonyms of lounge include footle, hang around, lallygag, linger, loaf, loiter, lollygag, lurk, mess about, mill around, tarry.

lounge (noun)	mill about (noun)
a room (as in a hotel or airport) with seating where people can wait
an upholstered seat for more than one person

lounge (verb)	mill about (verb)
sit or recline comfortably	move about in a confused manner
be about a place without any apparent purpose	be about a place without any apparent purpose