brain bucket

noun brain buckets · brain-bucket

1. humorous, idiomatic, sometimes A protective helmet, as worn, for example, by a motorcyclist, bicyclist, or soldier in combat. The Air Force not only makes up words and phrases (e.g., brain bucket for crash helmet) . . . .
2. dated The skull; the head. [H]e fetched me such a clip on top of my brain-bucket as to drive all my senses clear down into my boots.