bum vs dosser

bum and dosser both are nouns.

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

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

Other hyponyms of bum include street person.

bum (noun)	dosser (noun)
the fleshy part of the human body that you sit on	someone who sleeps in any convenient place
a vagrant
a person who is deemed to be despicable or contemptible
person who does no work

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

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