Brass neck/nerve
Definition 1 of 1
Pro Tip 1/3Context Matters
Use 'brass neck' to describe bold actions, often in a disapproving way, when someone ignores social norms. 
She had the brass neck to cut in line at the cinema.
Pro Tip 2/3Bold Rejection
'Brass neck' can suggest refusing to accept blame or embarrassment, even when it's expected. 
He showed a brass neck denying it was his mistake.
Pro Tip 3/3Often Negative
'Brass neck' is usually negative, implying someone is being rude or disrespectful in their boldness. 
He had the brass neck to complain about the gift.