triduan
An event lasting three days.
Pius IX has defined the sacred dogma, and the Catholic world has rejoiced, and Triduans, that is, three days of special joy and holy exercises, have been celebrated throughout the wide world, and continue to be celebrated in honor of the glad event.
Where it comes from
From Latin triduanus, from triduum (“space of three days”).
Adapted from the Wiktionary entry triduan (CC BY-SA 4.0).