Definition of rosehead:
(n) :
The head or blossom of a rose.
(n) :
A many-sided pyramidal head upon a nail.
(n) :
A nail with that kind of head.
(n) :
A circular or spherical nozzle or end to something that is perforated to allow the escape of liquid or gas.
(n) :
(dentistry, surgery) A bur or gouge that has a spherical head and curled blades, resembling the curled petals of a rose.
(n) :
(woodworking) A conical drillbit that has radiating blades.