bolster vs fill

bolster and fill both are nouns.

Word	Noun	Adjective	Verb	Adverb
bolster	Yes	No	Yes	No
fill	Yes	No	Yes	No

As verbs, fill is a hypernym of bolster; that is, fill is a word with a broader meaning than bolster:

Other hypernyms of bolster include fill up, make full.

bolster (noun)	fill (noun)
a pillow that is often put across a bed underneath the regular pillows	a quantity sufficient to satisfy
	any material that fills a space or container

bolster (verb)	fill (verb)
add padding to	become full
support and strengthen	make full, also in a metaphorical sense
prop up with a pillow or bolster	plug with a substance
	fill to satisfaction
	eat until one is sated
	fill, satisfy or meet a want or need or condition or restriction
	assume, as of positions or roles
	appoint someone to (a position or a job)
	occupy the whole of