1 [mathematics] The middle value of a set of values when they are ordered by rank. Half the values in a set are higher than the median, and half are lower. When there are two middle values (if the set has an even number of elements) the median is the mean of these two values.
2 [spatial statistics use for geostatistics] The location of a single x,y coordinate value that represents the median x-coordinate value and the median y-coordinate value for all features in a study area.