undermine

/ˌən-dər-ˈmīn/

verb

  1. to subvert or weaken insidiously or secretly

  2. to weaken or ruin by degrees

  3. to wash away supporting material from under

trying to undermine his political rivals

weaken enfeeble debilitate undermine sap disable mean to lose or cause to lose strength or vigor. weaken may imply loss of physical strength, health, soundness, or stability or of quality, intensity, or effective power. enfeeble implies a condition of marked weakness and helplessness.