Zero traffic pages are pages that are poorly written OR their titles have no SEO value OR the kw competition is too high etc etc.
This is true in terms of a lack of search traffic. But if your pages are getting no traffic at all - no one's linking them or sharing them socially or anything - it could also be people find the page not relevant to the rest of what your site's about.
Example: your site is about growing tomatoes, and it includes articles about growing them as well as sales pages with products that help. You include an article about donating excess tomatoes to local charities, but apparently your readers either aren't growing excess tomatoes, or they already have people to give them away to, or they already know about the charities, or they don't care about the charities. So no one visits this page.
This will overlap some with what Rasputin is talking about: your page on donating tomatoes to charity may be fantastic, but if people visiting your site feel it's out of place or not of interest, then it won't get much traffic.