Longman Dictionary of Contemporary English
washing-up liquid
noun
EXAMPLES FROM CORPUS
▪ After all, the best washing-up liquid in the world can't keep your skin as soft as we can.
▪ An organic alternative to proprietary sprays is a strong solution of soap or washing-up liquid in warm water.
▪ From the emotions It's nice of the Persil people to come up with a washing-up liquid.
▪ From the reason Persil washing-up liquid comes from the people who make Persil.
▪ I hope that's ozone-friendly washing-up liquid they're using.
▪ If the greenery is grimy add a drop of washing-up liquid.
▪ Washing dollies Warm water, washing-up liquid, scrubbing brush and cloths, plus waterproof dolls, are an irresistible combination.
Wiktionary
washing-up liquid
n. (context British English) The substance used to wash dishes.