Playing Garlic means the following:

Playing Garlic is a commonly used Chinese colloquialism, which means that a person acts as if he/she knows or understands something very well in words or behaviors, but in fact does not really know or does not really have the relevant knowledge and skills.

The foreign garlic in this word is an exotic vegetable, because in the past, onions were not grown in China, so people called it foreign garlic. Therefore, the word "pretending" means that when someone acts as if he or she knows or understands something well, he or she is actually just pretending, just like an onion, which is just a kind of outer shell and has no real knowledge and skills inside.

For example, if someone talks about a certain field of knowledge in front of you, but you find many mistakes and loopholes in what he says, then he is pretending. Or, if someone acts as if he is very experienced in front of you, but you find his behavior very unprofessional, then he is also pretending.

Playing Onion Sentence:

1. He plays onion all day long, thinking he's a learned man, but in fact he's only a half-baked one. Pretending to be an onion in this sentence means that when someone acts as if he or she knows or understands something very well, he or she is really just pretending.

Like an onion, it's just a kind of shell, with no real knowledge or skill inside. The idiom of half a bucket of water is used in this sentence to mean that someone's knowledge and skills are not deep, but only on the surface.

2. Don't pretend to be an onion in front of me, I can see all your little tricks. Pretending to be an onion in this sentence means that when someone is acting as if he or she knows or understands something very well, he or she is really just pretending. The use of the word tricks in this sentence means that the tactics or tricks someone uses are not very clever, just something childish.

3. He always pretends to be an onion, thinking that he is very experienced, but as a result he often makes mistakes at work. Pretending to be an onion in this sentence indicates that when someone is acting as if they are experienced, they are really just pretending. The use of the word mistakes in this sentence means that someone often makes mistakes at work, showing that his experience and skills are not sufficient.