What is an adaptor?
Adaptor (plumbing) definition - A specialized connector that allows the joining of different pipe styles in a plumbing system. It also helps connect different pipes, of different material, with one another.
Ideal Home Garden Explains
Plumbing adaptors are usually found in bathrooms and kitchens where water is running. Adaptors are commonly used for repairs when old pipes break or crack. Some adaptors can be screwed and tightened with a crescent wrench, others require glue, and metal based adaptors tend to require soldering.