To stir is to move ingredients in a dish around.
It can be done while preparing the dish, cooking the dish, or afterwards to help the dish cool faster.
The purpose is usually to either combine the ingredients, or to move them around so that they cook more evenly.
Stirring can be also used to form a whirlpool for poached eggs.
Stirring is usually a circular motion. Most right-handed people tend to stir in a clock-wise direction.
A more energetic form of stirring is called “beating”, which is designed to introduce air.
Literature & Lore
Stirring counter-clockwise has historically been seen as bad luck. In Scotland, doing so would ruin the oatmeal; in Italy, the pasta sauce. Ingredients for dark magic are stirred counter-clockwise, or “widdershin” or “withershins” as it’s sometimes referred to (from the old German word “widersinnen”, with “wider” meaning “against” and “sinnen” meaning “to move or go”.)
It’s a myth that Australians stir in a counter-clockwise direction.