peen (pēn) n. The end of a hammerhead opposite the flat striking surface, often wedge-shaped or ball-shaped and used for chipping, indenting, and metalworking. tr.v.
peened, peen·ing, peens To hammer, bend, or shape with a peen.
1683, "sharp or thin end of a hammer head, opposite the face," probably from a Scand. source (cf. Norw. dial. penn "peen," O.Swed. pæna "beat iron thin with a hammer"). Earlier as a verb, "to beat thin with a hammer" (1513).