A lap was a circuit around a room or other defined area.
In 2267, Captain James T. Kirk told Nyota Uhura to order the Columbus to open its course two degrees on every lap, in order to increase the likelihood of covering the entire planet's surface when searching for the Galileo. (TOS: "The Galileo Seven")
In 2371, Tuvok punished Chell with forty laps around a USS Voyager cargo bay for speaking without having been spoken to, amending it to 50 when he protested. While running on deck 13, Tuvok ordered Gerron and Chell to complete their run, as he, Henley, and Kenneth Dalby had lapped them three times. Later, Dalby spoke out about how he and his fellow ex-Maquis crewmembers were being treated, despite his belief that he'd likely get 200 laps for saying so. Henley complained to Chakotay about the Vulcan's "ridiculous" orders. (VOY: "Learning Curve")