washer vs washerwoman

washer and washerwoman both are nouns.

Word	Noun	Adjective	Verb	Adverb
washer	Yes	No	No	No
washerwoman	Yes	No	No	No

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

Other hyponyms of washer include laundryman, washerman, laundress, laundrywoman, washwoman, window washer, washman.

washer (noun)	washerwoman (noun)
a home appliance for washing clothes and linens automatically	a working woman who takes in washing
seal consisting of a flat disk placed to prevent leakage
someone who washes things for a living