Translation guide
The English phrase 'fold one's arms' can refer to a physical action or a metaphorical stance. In Japanese, different expressions are used depending on the nuance.
Describing the physical posture of crossing one's arms in front of the chest.
The most common and neutral way to say 'fold one's arms'. It literally means 'to cross one's arms'.
He was deep in thought with his arms folded.
a person standing with their arms folded
A slightly more formal or literary variant. Often used in written descriptions.
He was looking out the window with his arms folded.
Expressing the idea of standing by and doing nothing, often out of stubbornness or protest.
Literally 'to fold one's arms', but used idiomatically to mean 'to look on without doing anything', 'to stand by idly'. Often used in negative contexts.
You can't just fold your arms and watch when someone is in trouble.
He always folds his arms and never does anything on his own.
Similar to 腕をこまねく, but uses 'hands' instead of 'arms'. Also means to stand by idly.
Describing alternative ways of folding arms, such as behind the back or with a specific grip.
Be careful not to use 腕を組む when you mean the idiomatic 'fold one's arms and do nothing'. Use 腕をこまねく for that meaning. Conversely, 腕をこまねく is not used for the simple physical action.
Just folding your hands and watching won't solve the problem.
She folded her arms tightly and refused to listen.