It means HP adds the rel=noindex meta tag to your hub, which tells Google not to index the page. You can usually get it back to featured by making some simple changes. Adding a photo or a bit more text. Be warned that if the change is too trivial, it might go back to idle in a few weeks.
Whether or not it is worth editing idle hubs is something you have to decide. Many long-time writers here, including me, are simply moving idled hubs to other sites where they get more search traffic. It's not necessarily your hub that's the problem, but the fact the HP as a whole is not very "well-liked" by Google; HP articles don't rank as high search results any more.
I make a lot more per article per month on Infobarrel, about 5-6 times as much. I'm not an active member of Wizzley or Squidoo, but others also report their articled doing much better on those sites too. Just letting you know about your options.