In his dissenting opinion in Gonzalez v. Arizona,Judge Kozinski–no stranger to the Internet–relies on Wikipedia to define the “exclusive or.”

Indeed, it is well recognized that “or” can have multiple meanings, with the “exclusive or”—meaning one or the other but not both— being largely useful in symbolic logic rather than common parlance. Wikipedia, Exclusive or, http://en.wikipedia.org/wiki/Exclusive_or (last visited Aug. 21, 2010).

7Wikipedia gives the following example to illustrate the difference between the exclusive and the inclusive “or”: [I]t might be argued that the normal intention of a statement like “You may have coffee, or you may have tea” is to stipulate that exactly one of the conditions can be true. Certainly under many circumstances a sentence like this example should be taken as forbidding the possibility of one’s accepting both options. Even so, there is good reason to suppose that this sort of sentence is not disjunctive at all. If all we know about some disjunction is that it is true overall, we cannot be sure that either of its disjuncts is true. For example, if a woman has been told that her friend is either at the snack bar or on the tennis court, she cannot validly infer that he is on the tennis court. But if her waiter tells her that she may have coffee or she may have tea, she can validly infer that she may have tea. Nothing classically thought of as a disjunction has this property. This is so even given that she might reasonably take her waiter as having denied her the possibility of

having both coffee and tea.

. . . .

There are also good general reasons to suppose that no word in any natural language could be adequately represented by the binary exclusive “or” of formal logic. Wikipedia, Exclusive or, http://en.wikipedia.org/wiki/Exclusive_or (last visited Aug. 21, 2010).