The Collaborative International Dictionary
Snaphead
Snaphead \Snap"head`\, n. A hemispherical or rounded head to a rivet or bolt; also, a swaging tool with a cavity in its face for forming such a rounded head.
Wiktionary
snaphead
n. 1 A hemispherical or rounded head to a rivet or bolt. 2 A swage tool with a cavity in its face for forming such a rounded head.