Post Lunch Narcolepsy. The feeling you get at 3.00 in the afternoon when you're struggling to keep your eyes open at your desk at work.
Dave: "Woah, that girl in accounts looks half asleep!"
Alison: <nodding> "PLN."
Post Liturgy Nap. In Orthodox Christianity, services are very long, and frequently, there are new pews in Churches, requiring the faithful to remain standing and alert for long periods of time. After Church liturgy and coffeehour, parishoners often go home and have a Post Liturgy Nap.
After Liturgy, Sasha and Katherine went home for the usual PLN.