discordant couple n. a pair of long-term sexual partners, such as a married couple, in which one is infected with a sexually transmitted disease and the other is not. (source: Double-Tongued Dictionary)
Further reading
Aubrey in Waco, Texas, says her mother used to warn the kids against contracting honkus of the bonkus, a fanciful name for a contagious disease. This colloquial term probably comes from the words bonk and konk, meaning “to hit” or...