Priority Inversion
A scenario in scheduling in which a high priority task is indirectly preempted by a lower priority task effectively inverting the relative priorities of the two tasks.
Origin
Computer scientists Butler Lampson and David D. Redell first described the problem in a 1980 paper in Communications of the ACM. The issue became famous in 1997 when it caused repeated system resets on NASA's Mars Pathfinder lander — engineers fixed it remotely by enabling priority inheritance, a protocol proposed by Sha, Rajkumar, and Lehoczky in 1990.
Everyday Use
You need to finish an urgent report, but you can't because someone is using the only conference room for a low-priority meeting — and a third person's medium-priority task is blocking you from rebooking it. The urgent task waits while the trivial one runs. It happens in software, organizations, and daily life.