This is a definition most understood by photographers. Pixel shift is a double entendre. It refers to Photoshopping an image and shifting the pixels around to enhance the image. It also refers to the time of day that this usually occurs. A pixel shift isn't done during normal business hours but rather it runs late through prime time, party time and early morning.
A pixel shift usually occurs when there is a crunch or deadline that needs to be met at all costs. That cost is usually a lack of sleep for the photographer and stretches through the evening.
I have been pixel shifting all week, I am taking next week off.
I can get those images edited in time but it will be a pixel shift to do get it done.