Comment by likeclockwork

Pixel perfect means it looks EXACTLY like the design comp.

It goes completely out of the window if the browser window isn't the exact size of the mockup.

You might charitably say that pixel perfect means that the implementation intersects with the design comp at some specific dimensions but where are the extra rules coming from, then?

It's an archaic term that conflates the artifact produced by an incomplete design process (an artist's rendering of what the web page might look like) with the actual inputs of the development process (values and constraints).