double-decker—
1. a bus with an upper level:
- Ride the bus just to say you rode a double decker, but stick to the Tube for speed and ease of use.
2. a sandwich with two layers of filling:
- He was clearly more interested in eating a double decker and didn’t even have the decency to ask my name.
twin-deck—
1. part of a music center with two cassette or CD recorders in it:
- Make your own recordings with this twin deck CD recorder.
2. (attrib.) is used of aircraft that have an upper and a lower deck:
- This twin-deck aircraft will carry more than 500 passengers in a three-class configuration.