A snack is a small portion of food that is generally eaten between meals. Snacks come in a variety of forms, including packaged snack foods and other processed foods, as well as items made from fresh ingredients at home. Traditionally, snacks are prepared from ingredients commonly available at home without a great deal of preparation. Often, cold cuts, fruits, leftovers, nuts, sandwiches, and sweets are used as snacks. Snack foods are typically designed to be portable, quick, and satisfying. Processed snack foods, as one form of convenience food, are designed to be less perishable, more durable, and more portable than prepared foods. They often contain substantial amounts of sweeteners, preservatives, and appealing ingredients such as chocolate, peanuts, and specially designed flavors (such as flavored potato chips) .

In addition to food, "snack" can also be used as a verb, meaning to eat a snack.

It is worth noting that "snack" can also be used as an internet slang term that conveys that a person is considered attractive or sexy. However, this usage is not related to the food definition of "snack."