A "special adaptor" refers to a device or component that allows one thing to connect or work with another thing that it normally wouldn't be able to. It helps two incompatible things to work together. Full definition
When it comes to ports, the iPad doesn't have a leg to stand on, just a proprietary connector that requires special adaptors (and by special I mean expensive) to connect to a TV, camera, etc.. (the-ebook-reader.com)
The car seat attaches to the pushchair by clicking or slotting on it, or by using special adaptors. (jane-uk.com)
Connected by a special adaptor to the car audio system, music can be played without compromising the iPod's clear sound quality. (www2.mazda.com)