Vulcan expeditions were missions of exploration conducted by the Vulcans.
According to Commander Trip Tucker, every school kid on Earth had to learn about the famous Vulcan expeditions. In 2151, Sub-commander T'Pol asked him to name one of them; Tucker, who was unable to, noted that history wasn't a good subject for him. Tucker had mentioned the expeditions when T'Pol said she hadn't heard of the Human venture known as Terra Nova. (ENT: "Terra Nova")