1. immediately and with little provocation
get angry at the drop of a hat
The expression 'at the drop of a hat' means to be quick to act or do something. This idiom is used to refer to being quick to help somebody or to express an urgent desire to do something. However, it typically has negative connotations, often relating to an irrational demand or an emotional overreaction. It is common in both a social and professional context, and is similar to the phrases 'at a moment's notice,' and 'in a heartbeat.'