slacken vs dowse

slacken is not a noun while dowse is a noun.

Word	Noun	Adjective	Verb	Adverb
slacken	No	No	Yes	No
dowse	Yes	No	Yes	No

As verbs, dowse is a hyponym of slacken; that is, dowse is a word with a more specific, narrower meaning than slacken:

Other hyponyms of slacken include douse.

slacken (noun)	dowse (noun)
	searching for underground water or minerals by using a dowsing rod

slacken (verb)	dowse (verb)
become looser or slack	cover with liquid; pour liquid onto
make slack as by lessening tension or firmness	slacken
become slow or slower	use a divining rod in search of underground water or metal
make less active or fast	wet thoroughly