n. A cup of tea with milk and one teaspoon of sugar, where the milk is poured into the cup before the tea. Variations are ISO 0, with no sugar; ISO 2, with two spoons of sugar; and so on.
Like many ISO standards, this one has a faintly alien ring in North America, where hackers generally shun the decadent British practice of adulterating perfectly good tea with dairy products and prefer instead to add a wedge of lemon, if anything. If one were feeling extremely silly, one might hypothesize an analogous 'ANSI standard cup of tea' and wind up with a political situation distressingly similar to several that arise in much more serious technical contexts. Milk and lemon don't mix very well.