This phrase is kind of strong. It can be translated as follow
- Don’t mess with me!
- Don’t kid with me!
- Don’t joke with me!
In general, this phrase is used with anger and intention to stop people from bothering you. It can also be used to stop kids (students) from kidding around in a class setting.
1) ふざけるなよ！(Fuzakeru nayo)
Use this one among friends in a way sounds like “Hey stop it”
2) ふざけないでください！(Fuzakenaide kudasai)
This one is somewhat polite but as it was stated, this phrase has a strong meaning, use it with care! May be used in business setting but with extreme care.
3) ふざけんなよ！(Fuzaken nayo)
Use this one when you are furious. You may have heard it in movies when a Yakuza is threatening someone. “Fu” is pronounced so small and smooth that you don’t really hear it.