When it comes to a cow pie, let's just say you won't be asking for whipped cream or a scoop of vanilla ice cream. You may be asking for a shovel and a pair of rubber gloves, however, because it is one of many slang and colloquial terms for cow manure or cow dung. Cows spend much of their time contributing "pasture patties" and "meadow muffins" while grazing in open fields. Many of these contributions can become a little bit round and flat, which makes the "cow pie" reference eminently understandable.
The good news about a cow pie is that the cow's diet is usually high in fiber and grain, which means its offerings are a bit more self-contained than certain other barnyard residents. One that is left alone will usually dry out from exposure to the sun, then crumble into a healthy fertilizer for the grass and other plants.
This tendency for a cow pie to become dry and compact over time has lead to a few interesting sporting events. One of the most popular forms of pseudo-entertainment is a cow chip throwing contest. Contestants select a suitable candidate from a collection thoughtfully provided by the sponsors. Cow pie throwing is more art than science, but the goal is to fling said "meadow muffin" into the air and aim for distance. The winner is usually awarded something a little less odoriferous, and apparently the congratulatory handshake from the judges has been largely abandoned.
Most people, however, avoid coming into direct contact with a cow pie whenever possible. Visiting a farm often includes walking gingerly through a cow pasture, since stepping into dung can be a very unpleasant experience. Some have even been known to slip and fall after stepping in a larger slice, so due diligence is strongly suggested when visiting Old Bessie and her girlfriends at the local dairy farm.