slag off

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slag off (third-person singular simple present slags off, present participle slagging off, simple past and past participle slagged off)

1. (transitive) To purify by melting and removing slag.

   There is a lot of copper oxide, but I can remove that by melting everything and slagging it off.

2. (UK, Ireland, Commonwealth, slang, transitive) To talk insultingly to or about someone or something; usually one who is not present.
   • 2023 February 24, Michael Segalov, quoting Will Young, “Will Young: ‘I’m locked out of my social media because I get drunk and slag people off’”, in The Guardian‎^[1], →ISSN:

     There’s pressure to be a brand. I’m even locked out of my social media because I just get drunk and slag people off.

   • 2025 July 28, John Crace, “Sidekick Starmer can’t get a word in as The Donald dominates world’s most one-sided double act”, in The Guardian‎^[2], →ISSN:

     The Donald didn’t seem convinced and started slagging off the London mayor, Sadiq Khan. “He’s a friend of mine,” squeaked Starmer.