Select the most appropriate meaning of the given idiom.

Cudgel one's brain

To think hard

The most appropriate meaning of the idiom "cudgel one's brain" is to think hard.

It is a colloquial expression that means to use one's intelligence and concentration to try to solve a problem or come up with an answer. It is often used to describe someone who is struggling to think of something.

The other options are incorrect:

• Thinking about a debate: This is not the meaning of the idiom "cudgel one's brain."
• Not to think: This is the opposite of the meaning of the idiom "cudgel one's brain."
• To overthink: This can be the meaning of the idiom "cudgel one's brain," but it is not the most common meaning.