to turn upside down
01
to reverse the position of something, making what was on top now at the bottom and vice versa
Collocation
例
Can you turn the mattress upside down for even wear?
The magician turned the hat upside down, revealing a rabbit inside.
02
to examine something thoroughly
例
The detective turned the case upside down to find the crucial evidence.
The researcher turned the data upside down to uncover patterns.
