projecting ornamental molding resembling the head of a nail, used in early Gothic architecture. Nailheads were used to fasten nailwork to a door, ... Found on http://www.britannica.com/eb/a-z/n/3
the enlarged top of a nail, usually flattened but sometimes rounded. · an ornament that suggests or resembles the enlarged top of a nail. Found on https://www.infoplease.com/dictionary/nailhead