1. Synonym slap on the side. Especially used of add-ons for the late and unlamented IBM PCjr.
2. The IBM PC compatibility box that could be bolted onto the side of an Amiga. Designed and produced by Commodore, it broke all of the company's own design rules. If it worked with any other peripherals, it was by magic.
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Nearby terms: SICL « SICS « SICStus Prolog « sidecar » side-effect » Siemens » Siemens Nixdorf Informationssteme, AG