Nonsense, rubbish.
Dismisses a wrong statement ("Quatsch!") and describes silliness in general. "Quatsch machen" is to mess around. Mild enough for any company, which makes it very useful.
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Reading a definition isn't the same as saying it to someone. Lingo Kaiava is a voice tutor set to German — it uses Quatsch the way locals do, corrects you in the moment, and never "fixes" the way real people actually talk into textbook German.
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