Calotte

noun

1. A skullcap, especially one worn by Roman Catholic priests.
2. A plain skull-cap or coif of haircloth, satin, or other fabric, worn by the Roman Catholic clergy to cover the tonsure when exposed to drafts;
3. in England, by serjeants-at-law on their wigs.
4. In armor and costume, that part of any head-dress which covers closely the crown of the head: as, the calotte of the helmet.
5. Anything having the form of a small cap, as the cap of a sword-hilt.