[someone_here]

Any amount of material can be moved any distance with an infinitesimal amount of force, given enough time... or maybe I'm missing something.

[Zak]

It's the amount of energy required to lift one pound vertically by one foot, or the amount of momentum a one pound object gains by falling one foot in a vacuum.

[hugh3]

Much of the confusion here comes from the fact that a pound is used both as a unit of force and as a unit of mass.

This is one of the many reasons y'all should use SI.

[ErrantX]

Not quite; friction has it's say first :)