Noun
symmetric difference (plural symmetric differences)
(set theory) The set that contains all elements belonging to either of given two sets but not to the both; the relative complement of the intersection in the union of given two sets.
As another example, we can also consider the set of all finite or cofinite subsets of X, again with symmetric difference and intersection as operations. Source: Internet
A symmetric difference overlay defines an output area that includes the total area of both inputs except for the overlapping area. Source: Internet
Note that the symmetric difference of two distinct sets can have measure zero; hence the pseudometric as defined above need not to be a true metric. Source: Internet