The share of a plow, or that part which cuts the slice of earth or sod at the bottom of the furrow.

a sharp steel wedge that cuts loose the top layer of soil

The ploughshare is the part of the plough which cuts into the soil to form the furrow when ploughing.

The ploughshare and coulter, the basic essentials of a plough, indicates a person who farms the land, usually a tenant or 'feu' farmer rather than a landowner.