Ŭn'der-mīne', v. t.

v. t. [imp. & p. p. UNDERMINED; p. pr. & vb. n. UNDERMINING.]

1. To excavate the earth beneath, especially for the purpose of causing to fall or be overthrown; to form a mine under; to sap; as, to undermine a wall. “A vast rock undermined from one end to the other, and a highway running through it.” Addison.
2. 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.

He should be warned who are like to undermine him. Locke.