From Webster's Revised Unabridged Dictionary:
Un`der*mine" (?), v. t.
1. To excavate the earth beneath, or the part of, especially for the purpose of causing to fall or be overthrown; to form a mine under; to sap; as, to undermine a wall.
Example: A vast rock undermined from one end to the other, and a highway running through it. Addison.
2. Fig.: To remove the foundation or support of by clandestine means; to ruin in an underhand way; as, to undermine reputation; to undermine the constitution of the state.
Example: He should be warned who are like to undermine him. Locke.
Me again: That will say the second, figurative meaning: Sabotage