A polite refusal of any sort, such as "Oh, you're too kind, I couldn't possibly accept such a lovely fruitcake."
The 'original' Chinese rejection slip is a joke among writers. It's based on the rather 19th-century stereotype that all Asian people are crafty and never say what they really mean, but despite its canonical name, it's still a pretty piece of work:
"We have read your manuscript with boundless delight. If we were to publish your paper, it would be impossible for us to publish any work of a lower standard. And as it is unthinkable that, in the next thousand years, we shall see its equal, we are, to our regret, compelled to return your divine composition, and to beg you a thousand times to overlook our short sight and timidity."
Any similarly effulgent rejection can be referred to as a 'Chinese rejection slip', but watch your audience. The term could be seen as politically incorrect.