Top Definition
Acronym for Spark Ignition Direct injection

It's the gasoline form of direct injection originally used only on diesel engines, now being used on some gasoline engines. Improves efficiency and power output.

Fuel injectors used in direct injection systems are more expensive than standard fuel injectors due to requiring more durable materials to withstand higher temperatures as the fuel injector is placed right into the combustion chamber.
This new SIDI engine sure is powerful, and the fuel economy ain't to bad either.
by ionyou February 18, 2011
A Scottish farmer who has intimate (typicall sexual in nature) relationships with their sheepdogs. Created by the Irish as a way of insulting the Scottish. Many Scots find this extremely insulting to theirselves and their ancestors.
Your uncle is such a badass sidi.
You sidi!
Ewww, he's a sidi.
by harry23243 August 07, 2007
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