Literally, as in: Don’t Stain.
But that doesn’t make any sense, of course.
Instead let’s think about this word in the practical form.
When you make somebody mad because your bad decision is affecting them, they might tell you: ¡No Manches!
When you’re lying and pretty much everyone knows you’re lying. ¡No Manches!
When you take advantage of another for whatever reason. ¡No Manches!
Yup, it’s not a very positive phrase you want to be addressed to you very often, if at all.
According to our friends at the Urban Dictionary, there are three Mexican idioms that fit the bill for the definition of this word: 1) Stop kidding around. 2) Don’t jerk my chain. 3) No way or whatever.
I’d say it can also have some pretty aggressive and much uglier meanings in Spanish, but I’ll let you figure out what those are on your own.
Have you ever used this word?
What was your interpretation of it if you have?