sponge bath vs washup

sponge bath and washup both are nouns.

Word	Noun	Adjective	Verb	Adverb
sponge bath	Yes	No	No	No
washup	Yes	No	No	No

As nouns, washup is a hypernym of sponge bath; that is, washup is a word with a broader meaning than sponge bath:

sponge bath: you wash your body with a sponge or washcloth instead of in a bathtub
washup: the act of washing yourself (or another person)

Other hypernyms of sponge bath include bathing.

sponge bath (noun)	washup (noun)
you wash your body with a sponge or washcloth instead of in a bathtub	the act of washing yourself (or another person)
	the act of washing dishes