lan si lan yong linsi

Swear word among the chinese/canto/singlish community to describe someone who is cocky/arrogant

Example
Person1: I don't think you can pass your upcoming exams which is due next week. I hardly see you study at all
Person2: OF COURSE I CAN PASS. DON'T LOOK DOWN ON ME! PLEASE!
Person1: Can you please don't be lan si lan yong linsi

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