more or less vs just about

more or less and just about both are adverbs.

Word	Noun	Adjective	Verb	Adverb
more or less	No	No	No	Yes
just about	No	No	No	Yes

As adverbs, more or less and just about are synonyms defined as:

more or less and just about: (of quantities) imprecise but fairly close to correct

Other synonyms of more or less include about, approximately, around, close to, or so, roughly, some.

more or less (adverb)	just about (adverb)
(of quantities) imprecise but fairly close to correct	(of quantities) imprecise but fairly close to correct
to a small degree or extent