sosi pisos, which came from Russian language (rus.: соси писос), means "suck a dick": sosi - is a transliteration of the corresponding Russian word that is translated as "suck", and pisos - is a non-dictionary word which was coined by kids by transforming another Russian word "писюн" which could be translared in English as "prick", "pecker" or "
penis".
Expression sosi pisos became very popular as a
meme. It is usually printed on a picture of a grey stripped
cat that has laid its paws at the wooden crossbow which is a piece of some kind of a house furniture, possibly a locker or
table. Print "соси писос, мем" in
Google and you will find at once a picture of that
cat. Sometimes the original inscription "соси писос" at the
cat's picture is replaced with "ты знаешь, что делать", that is translated as "you know what to do", that of course mean "suck a dick".
In a publick
chat someone gives a picture of a "sosi pisos"
cat with the inscription:
"Guys, look after a
cat. I will come soon." Then those participant leaves the chat. This means that the person think the topic of the conversation is meaningless, and chat participants are assholes.