From The Collaborative International Dictionary of English v.0.48:
Undermine \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.
[1913 Webster]
A vast rock undermined from one end to the other,
and a highway running through it. --Addison.
[1913 Webster]
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.
[1913 Webster]
He should be warned who are like to undermine him.
--Locke.
[1913 Webster]