1. A helmet to protect the head and brain, as worn by (e.g.) skateboarders, motorcyclists, soldiers, etc. It may not be fashionable, but if you wear your brain bucket when you ride your motorcycle, it may just save your life. We've experienced a lot of heavy fire in this region, so all soldiers are required to wear their brain buckets at all times in the field.

2. A dated term for one's skull. She received a knock to her brain bucket after she slipped on the stairs.