wash-hand basin vs washbasin

wash-hand basin and washbasin both are nouns.

Word	Noun	Adjective	Verb	Adverb
wash-hand basin	Yes	No	No	No
washbasin	Yes	No	No	No

As nouns, wash-hand basin and washbasin are synonyms defined as:

Other synonyms of wash-hand basin include handbasin, lavabo, washbowl.

wash-hand basin (noun)	washbasin (noun)
a basin for washing the hands	a basin for washing the hands
	a bathroom sink that is permanently installed and connected to a water supply and drainpipe; where you can wash your hands and face