Definition of "throuple"

The Air Force veteran fatally shot by police during last week’s US Capitol riot had been in a “throuple” with her husband and their live-in girlfriend, according to reports.

2021 January 14, Tamar Lapin, “Ashli Babbitt, Air Force vet killed at Capitol, was in a ‘throuple’”, in New York Post‎, retrieved 2021-07-22

Nearly a year ago, I began dating two friends — I’ll call them Rachel and Dave — who were already themselves in a relationship. We all had no experience with polyamory. The throuple ended fairly quickly, with no one being at fault; the other two continued to date but broke up not too long afterward.

2023 April 21, Kwame Anthony Appiah, “Our Throuple Fell Apart. What Are the Rules of the Breakup?”, in The New York Times‎