A buffet was a meal where everyone served themselves from a table full of food.
In 2370, after Byleth requested to have more food served to him, Beverly Crusher explained that the meal was a buffet and that everyone got their own food. Regardless, the Iyaaran wished to be served, and Worf complied, much to his own annoyance. (TNG: "Liaisons")
Later that year, a buffet was held to welcome a newly promotedRo Laren back to the USS Enterprise-D. Among the offerings were Bajoranforaiga. (TNG: "Preemptive Strike")
In 2373, Neelix had a Klingon Breakfast Buffet on USS Voyager. (VOY: "Fair Trade")