sap

weaken, enfeeble, debilitate, undermine, sap, cripple, 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.

• • a disease that weakens the body's defenses

enfeeble implies a condition of marked weakness and helplessness.

• • enfeebled by starvation

debilitate suggests a less marked or more temporary impairment of strength or vitality.

• • the debilitating effects of surgery

undermine and sap suggest a weakening by something working surreptitiously and insidiously.

• • a poor diet undermines your health
• • drugs had sapped his ability to think

cripple implies causing a serious loss of functioning power through damaging or removing an essential part or element.

• • crippled by arthritis

disable suggests bringing about impairment or limitation in a physical or mental ability.

• • disabled by an injury sustained at work