...is napping. Forty winks. Catching a few zeds. Or as the Brit pater familias always put it, with that strange human reluctance to admit that we're actually going to sleep during daylight hours: "Going upstairs to contemplate the Mysteries of the Infinite."
I am now firmly of the opinion that remaining fully awake through an entire afternoon is against human nature, all religions and the inherent mechanical laws of the Universe.