Slag off

British Slang

Definition

To harshly criticize or speak disparagingly about someone or something; to bad‑mouth.

Examples

"After the gig, he went on social media to slag off the band for their sloppy performance."

"Don’t slag her off just because she got the promotion—you don’t know the full story."

"The critics lined up to slag off the sequel, calling it lazy and unnecessary."