A pailful is the amount that fills a pail, which is another word for a bucket. If you need to water a garden and you fill your bucket to the brim with water, you're carrying a pailful of water. If you're picking blueberries and manage to fill your entire bucket, you've gathered a pailful of berries.

The word works like cupful, handful, or spoonful: it describes a quantity based on the container. When a recipe calls for two cupfuls of flour, it means two full cups. When someone mentions carrying three pailfuls of sand to build a sandcastle, they mean three full buckets' worth.

You'll often see this word in older stories and fairy tales. In many folktales, characters carry pailfuls of water from wells or streams, since people once had to fetch all their water by hand before indoor plumbing. Even today, if you're washing a car, mopping a floor, or doing anything that requires hauling water or other materials by the bucketful, you're dealing in pailfuls.