noun An Ancient Greek racecourse, especially, the Olympic course for foot races.
noun Synonym of stadion, a Greek unit of length equivalent to about 185 m.
noun A kind of telemeter for measuring the distance of an object of known dimensions, by observing the angle it subtends.
noun A graduated rod used to measure the distance of the place where it stands from an instrument having a telescope, by observing the number of the graduations of the rod that are seen between certain parallel wires (stadia wires) in the field of view of the telescope.