Definitions
1.VerbTo dig underneath (something), to make a passage for destructive or military purposes; to sap. .mw-parser-output .defdate{font-size:smaller}
2.VerbTo weaken or work against; to hinder, sabotage."The war efforts were undermined by the constant bickering between the allies."
3.VerbTo erode the base or foundation of something, e.g. by the action of water.
4.VerbTo regard an object as the sum of the parts that compose it, in object-oriented ontology.