shirker vs bum

shirker and bum both are nouns.

Word	Noun	Adjective	Verb	Adverb
shirker	Yes	No	No	No
bum	Yes	Yes	Yes	No

As nouns, bum is a hypernym of shirker; that is, bum is a word with a broader meaning than shirker:

shirker: a person who shirks his work or duty (especially one who tries to evade military service in wartime)
bum: person who does no work

Other hypernyms of shirker include do-nothing, idler, layabout, loafer.

shirker (noun)	bum (noun)
a person who shirks his work or duty (especially one who tries to evade military service in wartime)	the fleshy part of the human body that you sit on
	a vagrant
	a person who is deemed to be despicable or contemptible
	person who does no work

shirker (adjective)	bum (adjective)
	of very poor quality; flimsy

shirker (verb)	bum (verb)
	ask for and get free; be a parasite
	be lazy or idle