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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]