What is "leaving undone"

Usage examples of "leaving undone".

The people here have no urgencies, no capacity for sustained endeavor, but merely tackle things by fits and starts, leaving undone whatever fails to hold their interest, and so, by witlessness and improvidence, escape many of the errors of accomplishment.

As for El Salvador -- the book that didn't get done, the book I was leaving undone -- well, it was too late now.

They had helped clear up the dinner dishes, and discussed with Pop the few assignments they would be leaving undone by taking off on their vacation a few days earlier than they had expected.