mug up vs grind away

mug up and grind away both are verbs.

Word	Noun	Adjective	Verb	Adverb
mug up	No	No	Yes	No
grind away	No	No	Yes	No

As verbs, mug up and grind away are synonyms defined as:

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

mug up (verb)	grind away (verb)
study intensively, as before an exam	study intensively, as before an exam