crown of the head; top of the skull
Refers to the flat upper part of the cranium. A somewhat technical or anatomical term; in everyday conversation, 頭のてっぺん or 頭頂部 are more common.
I bumped the top of my head.
In anatomy, 頭の鉢 refers to the upper part of the skull.
Compound of 頭 (atama, 'head') + の (no, possessive particle) + 鉢 (hachi, 'bowl'), literally 'bowl of the head', referring to the rounded, bowl-like shape of the top of the skull.