hammer blow

Festing waited anxiously, because the wheels of a locomotive when driven hard strikes what is called a hammer blow.

What a sledge-hammer blow (coup de massue) that has been,” he wrote to his brother; “my only hope was from France.

A sledge-hammer blow from Dolph's fist grazed his jaw as he sprang aside.

Just as she reared up for a sledge-hammer blow, the boy whirled squarely about and shot away to left.

Thrown off his balance by the boy's quick avoidance of the sledge-hammer blow, Kennell stumbled forward.