Ken Adams reports on a couple of judicial screeds against the term and/or. The learned judges in question would hold that the proper term is X or Y or both, not X and/or Y. In the words of one judge, and/or is the refuge of “the lazy, the ignorant, and the harried …” The other judge scolded that and/or “is an indolent way to express a series of items that might exist in the conjunctive, but might also exist in the disjunctive.”
The second judge (no slave to brevity) continued, “the drafter could express a series of items as, ‘A, B, C, and D together, or any combination together, or any one of them alone.'” Um, sure.
Count me in the camp of those who insist that snd/or is a perfectly fine shorthand, thank you very much. I suspect, but couldn’t prove, that it’s universally and correctly understood.* Language was made for man, not man for language.
In computer engineering and-programming, the term XOR has long been used as a shorthand to make it clear the writer means exclusive-or, as in X or Y but not both,. Given the wide acceptance of and/or as meaning the inclusive or, there’s no reason lawyers and laypeople shouldn’t likewise use it to be clear about their intent.
(The term and/or isn’t used in computer engineering or -programming, because the simple or is already accepted as inclusive. )
* Ken also warns, as does UT Law School legal-writing prof Wayne Scheiss in his comment, against using and/or in contexts where it’s substantively wrong.