IPA: /ˈkʌplɪŋ/
KK: /ˈkʌplɪŋ/
A device or method used to connect two things together, often in a mechanical or electrical context.
The engineer installed a coupling to connect the two pipes securely.
Coupling is formed from "couple" (from Old French *cople*, meaning a pair or two things joined together) and "-ing" (a suffix used to indicate the action or process of). The word "coupling" refers to the action or process of joining two things together as a pair.
Think of a 'pair' ('couple') being 'joined together' — that's what coupling means.