slim vs melt off

slim is an adjective but melt off is not an adjective.

Word	Noun	Adjective	Verb	Adverb
slim	No	Yes	Yes	No
melt off	No	No	Yes	No

As verbs, slim and melt off are synonyms defined as:

Other synonyms of slim include reduce, slenderize, slim down, thin.

slim (adjective)	melt off (adjective)
small in quantity
being of delicate or slender build

slim (verb)	melt off (verb)
take off weight	take off weight