23 C.F.R. § 1208.3
As used in this part:
Alcoholic beverage means beer, distilled spirits and wine containing one-half of one percent or more of alcohol by volume. Beer includes, but is not limited to, ale, lager, porter, stout, sake, and other similar fermented beverages brewed or produced from malt, wholly or in part or from any substitute therefor. Distilled spirits include alcohol, ethanol or spirits or wine in any form, including all dilutions and mixtures thereof from whatever process produced.
Public possession means the possession of any alcoholic beverage for any reason, including consumption on any street or highway or in any public place or in any place open to the public (including a club which is de facto open to the public). The term does not apply to the possession of alcohol for an established religious purpose; when accompanied by a parent, spouse or legal guardian age 21 or older; for medical purposes when prescribed or administered by a licensed physician, pharmacist, dentist, nurse, hospital or medical institution; in private clubs or establishments; or to the sale, handling, transport, or service in dispensing of any alcoholic beverage pursuant to lawful employment of a person under the age of twenty-one years by a duly licensed manufacturer, wholesaler, or retailer of alcoholic beverages.
Purchase means to acquire by the payment of money or other consideration.
23 C.F.R. § 1208.3