Simple past tense and past participle of undermine.(verb)
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Use "undermined" in a sentence
"They tried to define him as a Carter, a label undermined when health care reform passed."
"I will keep looking for specific numbers but based on my knowledge of the field of meteorology in general I would not expect more than a thousand scientists world-wide are working on this topic and the number of those people whose work would be undermined is a fraction of that."
"The report found, among other defects, that the Iraqi High Tribunal was undermined from the outset by Iraqi government actions that threatened the independence and perceived impartiality of the court."