filling vs refilling

filling and refilling both are nouns.

Word	Noun	Adjective	Verb	Adverb
filling	Yes	No	No	No
refilling	Yes	No	No	No

As nouns, refilling is a hyponym of filling; that is, refilling is a word with a more specific, narrower meaning than filling:

Other hyponyms of filling include renewal, replacement, replenishment.

filling (noun)	refilling (noun)
the act of filling something	filling again by supplying what has been used up
the yarn woven across the warp yarn in weaving
(dentistry) a dental appliance consisting of any of various substances (as metal or plastic) inserted into a prepared cavity in a tooth
a food mixture used to fill pastry or sandwiches etc.
flow into something (as a container)
any material that fills a space or container