Definition
“Slag off” is a phrasal verb that means to criticise someone or something in an unpleasant way.
For example – “I don’t want to be friends with her anymore because I heard her slagging off my mum.”
“Slag” can be used as a verb by itself and has the same meaning also.
Clip 1
Clip 1 is from the British comedy series Peep Show and the male character Mark was saying some derogatory things about his girlfriend Dobby to impress his sexist boss and co-worker. Dobby overhears this and storms off. Mark tries to stop her from leaving but she tells him she would rather go to their mutual friend’s place Super Hans because no one will slag her off behind her back.
Clip 2
The second clip is from the documentary Coldplay: A Head Full Of Dreams. The lead singer of Coldplay Chris Martin is talking about how much the band cares about performing well and releasing good music. He says “We care when people slag us off” as a way of saying they care when they receive criticism and want to prove people wrong.
Clip 3
The third clip is from the British mockumentary series This Country. The character Slugs tells Kurtan that he knows he’s been “slagging him off” (talking badly about him) but before Kurtan has a chance to reply Sluggs says to him “It’s alright. I slag you off too.” Kurtan is shocked and asks Sluggs who he slags him off to and is even more shocked when Sluggs tells him he slags him off to Kerry, Kurtan’s sister. Kerry tells Kurtan it’s because he can be quite annoying sometimes and this prompts Kurtan to tell his sister that he never slags her off.