Previous definitions:
1.
A dairy product made by churning cream until the milk fat has collected into a solid. In the U.S., the fat percentage has to be 80% or greater for the product to be sold as butter.
As defined by Michael Chu
on June 22, 2008
2.
Made by churning cream until it becomes solid. It consists of milk fat, water, and milk solids. Butter can be purchased salted or unsalted, and can be used by itself as a spread, or in cooking both sweet and savory foods.
As defined by Mechanical Turk
on June 09, 2011