I saw this tweet
WATCH: 3-YR-OLD CHESS PRODIGY CRIES AFTER GETTING RINSED ON RUSSIAN TV
and couldn't make sense of it, my mother tongue not being English did not help the situation, thus I'm here... Thanks for answers
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It is British slang and it means he was beaten badly. Humiliated, ruined, destroyed.
As Wiktionary says (meaning 3):
rinse (v.) (Britain, slang) To thoroughly defeat in an argument, fight or other competition.