tough nut

Altogether, it is a very tough nut to crack, and the force at our disposal none too strong for the work that lies before it.

Drank rum by the hogshead, pounded his wife till she left him, and was a tough nut gin'rally.

"H'm, and a pretty tough nut to crack," threw in Cleek with a little laugh.

Point is that Houck, who always was a t-tough nut, has gone bad since the boys rode him on a rail.

This particular member of the force was an unusually tough nut to crack.