Longman Dictionary of Contemporary English
Douglas Harper's Etymology Dictionary
Wiktionary
n. (cx often attributive English) the practice of serving oneself, usually when purchasing items
WordNet
adj. of or denoting an establishment (a restaurant or shop etc.) where customers serve themselves
n. the practice of serving yourself (as in a grocery or cafeteria)
Wikipedia
Self service is the practice of serving oneself, usually when purchasing items. Common examples include many gas stations, where the customer pumps their own gas rather than have an attendant do it (full service is required by law in New Jersey, Oregon, and Richmond, British Columbia, but is the exception rather than the rule elsewhere). Automatic Teller Machines (ATMs) in the banking world have also revolutionized how people withdraw and deposit funds; most stores in the Western world, where the customer uses a shopping cart in the store, placing the items they want to buy into the cart and then proceeding to the checkout counter/aisles; or at buffet-style restaurants, where the customer serves their own plate of food from a large, central selection.
Usage examples of "self-service".
On the Saturday following my traumatic weekend, I purchased an adjustable spanner, a pair of pliers and a craft knife in a self-service store devoted to motoring accessories.
She led him further down the street, in the direction the girl had fled, then opened a door sandwiched in between a boarded-up storefront that had once sold groceries and what looked like a combination self-service laundrey and betting parlor, judging by the number of frowsy, bitter-faced women playing cards and the even greater number of men rolling dice while the machines jigged and bumped and rattled their syncopated rhythm, cleaning what few clothes these people owned.
I've dealt with a couple of fender benders, some heated words at the self-service pumps, and a kid who was left behind at the SuperSaver.
Highway 68 unrolled before us, turning its way through miles of woods and splitting the little towns that were there and gone in a slow blink, each one with its bar and its self-service gas station: New Sharon, Ophelia, West Ophelia, Ganistan (which had once been Afghantistan, strange but true), Mechanic Falls, Castle View, Castle Rock.
Without considering why he was doing this, he stopped at a shopping complex that covered acres and acres, miles maybe, and took the Bressler papers into an office supply warehouse store where he used a self-service copy machine and made copies of everything.