1. The number of blows required to drive an object into soil.
2. In soil borings, the number of blows required to advance a sample spoon 6 in. (15.2 cm) or 12 in. (30.5 cm).
3. In pile driving, the number of blows required to advance .the pile 12 in. (30.5 cm) or the number of blows per unit distance of advance.