What's mean a word "lop"
I have heard this word a lot at animated movie "Wakfu"
"C'est un lop" - witches said when they kidnapped a guy
"Cette cervelle de lop"
My French is poor. It would be better to explain in English or even in Russian ;-)

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Well, "lop" in French doesn't exist. It is a word created by the authors. "Cervelle de lop" is more or less an insult, probably not very unkind, but an insult nevertheless.

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I don't know what "lop" is, perhaps you mean "loup" ?

"C'est un loup" means "It's a wolf"
"Cette cervelle de loup" means "This wolf brain"

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It's a rope or cable which makes a circle around a neck. Sorry I've confused perceiving the word as loop