weed-whacker vs weeder

weed-whacker and weeder both are nouns.

Word	Noun	Adjective	Verb	Adverb
weed-whacker	Yes	No	No	No
weeder	Yes	No	No	No

As nouns, weed-whacker and weeder are synonyms defined as:

weed-whacker (noun)	weeder (noun)
a hand tool for removing weeds	a hand tool for removing weeds
	a farmhand hired to remove weeds