mug up vs bone

mug up is not a noun while bone is a noun.

Word	Noun	Adjective	Verb	Adverb
mug up	No	No	Yes	No
bone	Yes	Yes	Yes	No

As verbs, mug up and bone are synonyms defined as:

Other synonyms of mug up include bone up, cram, drum, get up, grind away, swot, swot up.

mug up (noun)	bone (noun)
	a shade of white the color of bleached bones
	rigid connective tissue that makes up the skeleton of vertebrates
	the porous calcified substance from which bones are made

mug up (adjective)	bone (adjective)
	consisting of or made up of bone

mug up (verb)	bone (verb)
study intensively, as before an exam	remove the bones from
	study intensively, as before an exam