slaughterer vs knacker

slaughterer and knacker both are nouns.

Word	Noun	Adjective	Verb	Adverb
slaughterer	Yes	No	No	No
knacker	Yes	No	No	No

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

slaughterer (noun)	knacker (noun)
a person who slaughters or dresses meat for market	someone who buys up old horses for slaughter
	someone who buys old buildings or ships and breaks them up to recover the materials in them