Definition of "retractable"

Features such as trackless doors, mercury-type door interlocks, roof-mounted door fault indicator lights, rubber window glazing, improved retractable shoegear and a modified electro-pneumatic brake system designed to facilitate maintenance and improve reliability, which have proved their worth on the prototype trains, are continued in the new stock.

1960 February, “The first of London's new Piccadilly Line trains is delivered”, in Trains Illustrated, page 94

He says the company's FLIRT design, in particular its retractable steps, provides greater accessibility, while the technology is highly innovative and reliable.

2021 May 19, David Clough, “Swiss precision meets UK growth”, in RAIL, number 931, page 57

Somewhere in the cosmos, he said, […] there was also a planet entirely given over to Biro life forms. […] Veet Voogajig suddenly claimed to have found this planet, and to have worked there for a while driving a limousine for a family of cheap green retractables […]

1979 October 12, Douglas Adams, chapter 21, in The Hitchhiker’s Guide to the Galaxy, London: Pan Books