washbasin vs wash-hand basin

washbasin and wash-hand basin both are nouns.

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

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

Other synonyms of washbasin include handbasin, lavabo, washbowl.

washbasin (noun)	wash-hand basin (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