The occurrence of 2 or more people saying the same exact phrase at the same time.
But, instead of one of the participants exclaiming, "Jinx!" another person may exclaim "Jinx Hijack!" and "Hijack" the jinx from the victims, thus making them speechless.
{10:10:10 p.m.} Jack: I sure am hungry.
{10:10:10 p.m.} Brad: I sure am hungry.
{10:10:11 p.m.} Cecil: Jinx Hijack!