Peen

Peen may refer to:
 * Part of the head of a hammer, as in a ball-peen hammer (also ball-pein, or ball and pein)
 * Peening, the changing of a metal's properties by impacting its surface
 * Shot peening, bombarding metal parts with small spherical media
 * Laser peening, focusing lasers on the surface of a metal part
 * Peening (scythe blade), peening a scythe or sickle blade as a step in sharpening it
 * Steel Belt: Shot Peening, an innovative remedial solution for deformed steel belts
 * A slang term for the penis