1) Debilitate 2) Drain 3) Emaciate 4) Impair 5) Weaken 1) Debilitate 2) Drain 3) French word used in English 4) Make weak 5) To make feeble 6) Weaken 7) Weaken or debilitate 
• (v. t.) To make feeble; to deprive of strength; to reduce the strength or force of; to weaken; to debilitate.
En·fee'ble transitive verb [ imperfect & past participle Enfeebled ; present participle & verbal noun Enfeebling .] [ Old French enfeblir , enfeiblir ; prefix en- (L. in ) + feble , French faible...
Enfeeble: To make feeble or weaken. Years of chronic illness may leave someone enfeebled. The word enfeeble is not often used in medicine, perhaps because of a negative connotation of the word.
[v] - make weak
debilitate verb make weak; `Life in the camp drained him`
to make feeble; weaken: That bout of pneumonia enfeebled him.