sta·di·a 1 
(stādē-ə)
(stādē-ə)n.
1.
a. A telescopic instrument having two parallel lines through which intervals on a calibrated rod are observed, used to measure distances.
b. The parallel lines in this instrument.
c. The calibrated rod so used.
2. The technique of measuring distances with this instrument.
[Italian, probably from Latin, pl. of stadium, a unit of length; see STADIUM.]