This is a versatile word. Its most common usage as a verb refers to reading 2/3 of a book, then stopping. It can also be used to refer to doing 2/3 of anything and then stopping, or as a noun.
The second usage of Pernick centers around late
night walks, ie. to go on a Pernick. The
walk is usually
long and meandering, with no specific destination in mind.
The third and final usage of the word is as a verb relating to spirited debate. If you thrashed someone in a passionate,
well-thought-out debate, you Pernicked them.