I scoured OED-online for this word already, which my dad claims exists, but I think he's imagining things: a word that describes two letters, A and B, crossing each other midway, such that A was going to B and B to A. Let me know if this word exists, but if not, maybe sharing fancy words for postal events, like this one I got from the USPS glossary of terms, will make it all worthwhile:

à découvert - (French) Universal Postal Union term for open transit mail (mail that crosses U.S. borders while en route from one foreign country to another) that is in unsealed containers.

Also, "être à découvert" supposedly means to overdraft your bank account in French. The respondent below makes clear why à découvert applies to 'unsealed' containers.

Thanks all!

Last edited by Pfhyde; 03/27/2009 5:00 PM.