IPA: /ˈwiːkənər/
KK: /ˈwiːkənər/
A person or thing that makes something weaker or less strong.
The weakener in the chemical process reduced the strength of the material.
Weakener → It is formed from "weak" (from Old English *wēac*, meaning lacking strength) and "-er" (meaning a person who). A weakener is a person or thing that causes weakness or diminishes strength.
Think of someone or something that makes you 'weaker' — 'weak' means lacking strength, and '-er' indicates a person or thing that does that.