washer vs washerman

washer and washerman both are nouns.

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

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

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

washer (noun)	washerman (noun)
a home appliance for washing clothes and linens automatically	a man who operates an industrial washing machine
seal consisting of a flat disk placed to prevent leakage
someone who washes things for a living