1. weakened or damaged gradually, especially someone’s confidence, authority, or effectiveness
Usage: past tense and past participle of ‘undermine’
2. dug or wore away the foundation or base of something
Usage: past tense and past participle of ‘undermine’; literal sense

Examples

• The scandal undermined the politician’s credibility.
• Her constant criticism undermined his self-confidence.
• The flood waters undermined the bridge’s foundation.
• His authority was undermined by the leaked documents.
• The river had undermined the riverbank over many years.
• The team’s morale was undermined by poor leadership.
• Erosion had undermined the coastal cliffs.