When one takes a nap while sitting on the toilet. The shnap generally occurs at the work place and is the result of over eating, a bad hangover, boredom or a combination of the three. In order for one to take a shnap, he/she does not need to actually take a shit. The purpose of the shnap is that toilet may be the only place an employee can nap during the day.
I was so hungover on Friday that I went and took a shnap around lunch time. When I woke up 15min later I tried to stand up, but my legs were completely asleep, so I sat down and took another shnap.
The act of a person having a shit prior to going for a nap. This is usually done after a night of heavy binge drinking or a morning of strenuous activities.
Leigh felt that going for a "shnap" before going to her parent in laws house was completely necessary, not only will she be refreshed but would also feel no urges to go for number 2 time whilst there. One may consider this as a tactical "Shnap"