1. a device that connects two railroad cars together
Usage: railroad terminology
2. a device or mechanism that joins or connects two things together
Usage: general mechanical term

Examples

• The train engineer checked each coupler before departure.
• A broken coupler caused the freight cars to separate.
• The mechanic replaced the damaged coupler on the locomotive.
• Modern couplers automatically lock when train cars are pushed together.
• The pipe coupler joined the two sections of the water line.
• He used a coupler to connect the garden hoses together.