A simple skullcap or cervelliere which protects only the top of the head, in contrast to a greathelm or other helmet that would protect the whole head.

Any necrosis caused by exposure to ionizing radiation.

present participle of nesslerize

(firearms) A ringlike groove, such as that around the cylinder of an elongated bullet for small arms to contain a lubricant, or around the rotating band of a gun projectile to lessen the resistance...