meaning of peen
1. A round-edged, or hemispherical, end to the head of a hammer or sledge, used to stretch or bend metal by indentation.
2. The sharp-edged end of the head of a masons hammer.
3. To draw, bend, or straighten, as metal, by blows with the peen of a hammer or sledge.
4. the part of a hammerhead opposite the flat striking surface may have various shapes