Written on the page "residuo" as a meaning :
"La madre del vino son los "posos" y sedimentos formados por las impurezas de la uva y los restos de levadura".
That word must be written with "z" = "pozos".
I'good in grammar and etc. I studied Interpreter in English- Spanish
Thanks for your report. If you look up poso in the WordReference dictionary, you'll see that one of the meanings is "dregs" in the sense of sediment in wine. So it appears that the sample sentence is correct.
Nevertheless, we appreciate your help with building a first-class online reference tool.