Oral referred to ingestion through the mouth.
Some drugs were taken orally. In 2268, Doctor Leonard McCoy ordered that the theragen derivative antidote be given orally or intravenously to every member of USS Enterprise's crew. (TOS: "The Tholian Web")
In 2374, The Doctor told Seven of Nine that she would have to begin eating and drinking again. Seven protested that "Oral consumption is inefficient." The Doctor agreed, saying it was also unnecessary if you were a hologram, but that Human physiology required it. (VOY: "The Raven")