Simple past tense and past participle of slag.(verb)
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Use "slagged" in a sentence
"Um ... if this is the way you "deal with libs", maybe you're being "slagged" for your utter incoherence."
"Victor has told Nick that he does not think any of the other housemates have "slagged" them off despite the pair spending lots of time with each other."
"I just read a really long piece on him in the Philly newspaper, and it was loving, but kind of slagged off his second and third books."