IPA: /ɪnˈfiːbəl/
KK: /ɪnˈfibəl/
To make someone or something weak or less strong.
The long illness began to enfeeble him, leaving him unable to perform daily tasks.
Past: enfeebled
Past Participle: enfeebled
Enfeeble is formed from "en-" (meaning to cause to be) and "feeble" (from Old French *feeble*, meaning weak). The word means to cause someone or something to become weak or weaker.
Think of 'causing to be' ('en-') weak ('feeble') — that's why enfeeble means to make weak.