Definition of butter pat : a piece of butter formed into a ball or other ornamental shape for table use or an individual square cut from a quarter-pound stick of commercial butter.
There is no such thing as a pad of butter. If someone uses that term in their recipe, what they really mean is a “pat” of butter. Saying a “pad” of butter is a mistaken word used in place of a correct word that sounds a lot like the correct word. A pat is typically one teaspoon to one tablespoon.
There's no uniform size or quantity of butter provided in a pat. Most pats, however, contain between 1/3 and 1/2 tablespoons of butter. (That's about 1 to 1.5 teaspoons.) If you wanted to make your own pats—to serve at a dinner party, say—a good size is 1″x1″ square, and about 1/3″ thick.
The most common pat of butter, the square, contains about half a tablespoon. Smaller pats, often the tiny tubs, are about 1/3 tablespoon. Depending on the package size, there can be 1 to 3 pats of butter in a tablespoon.
Dry ingredients are ones that don't level out: flour, sugar, nuts, powders of all sorts including spices lumps, clumps, solids, butter, spreadable fats, and so on.
There's nothing more American than peanut butter and jelly – except for one small detail: Peanut butter isn't actually American at all. It's Canadian. It's widely assumed George Washington Carver, the American botanist, was the creator of peanut butter because of his tireless promotion of peanuts.