You'll probably also hear it called "pillar humping," "LOSing," or a few other choice terms. How much invective is behind the phrase will probably depend on whether the Druid's opponent is winning or losing, and with what regularity that's happening. What all these phrases refer to is this: getting behind obstacles to block your opponent's Line of Sight, and thus keeping them from shooting you.
Part of getting the bang from your buck while poledancing, however, is understanding Line of Sight itself. And while it may seem like grade school geometry, placement and movement around an obstacle can radically change a game. Where you are behind your obstacle will affect how quickly you can regain LOS on your partner, and how easily your opponent can get LOS on you. Remember: that second part is what you're trying to avoid.
Let's create a hypothetical arena that's just a box -- no obstacles at all. If you stand in the middle of it, you can see absolutely everything around you.
While you have perfect line of sight on everyone else in the arena, they also have perfect line of sight on you. The good news of this situation is that you are in a position to do anything to your partner and opponents that you wish -- assuming you're not getting pounded. The bad news is that you would definitely be getting pounded if you're just standing around in the open. You'd likely to be under some form of crowd control, or otherwise just very quickly getting killed.
Now let's re-imagine our hypothetical arena. We're going to place a single obstacle in it for you to duck behind. We're also going to place a Warrior in the arena with you, so that we can play with positioning.
The black area, obviously, is where you do not have Line of Sight. You can not affect, or be affected by, anything in that black zone. And as you pivot around the pillar, the black zone pivots with you in similar fashion.
From this obstructed vantage point, you're free to heal yourself, buff up, and drink some "Arena water." As a general rule, you want to keep anyone who's trying to hurt you -- whether they're trying to damage you, interrupt you, or crowd control you -- in the black. And, if it's at all possible, you want to keep your partner(s) out of it.
This can be a pretty tall order, and this is where a druid's vast toolbox of defenses come into play. "Stick and move." Drop an instant heal, then disappear behind your pillar. Consciously work to only come out when you have to do so, when revealing yourself will make a difference to the outcome of the match.
It's incumbent on your partner to help you manage the situation -- you are a team, and your partner needs to be just as aware of your placement and LOS as you are. Put a raid marker over each of your heads. You'll be able to see that marker through people, objects, and distance. In this way, it'll help you both be aware where you are, and where you're about to go. Stay active in voice chat -- simple words like "I'm moving" and "Breaking LOS to drink" will go a long way towards your situational awareness.
Crowd control (Cyclone or Entangling Roots) will help you control your LOS. If someone's on top of you, drop a CC on them, and get behind a different pillar. Hopefully, by the time they're free and gunning for you again, your partner will be in a position to help.
Poledancing does take practice, but is key to getting high ratings as a Druid. As has been said, mobility is your key. What's more, it's mobility behind places where they can't hurt you -- but you can still act. There's no reason to be completely idle. Ultimately, practicing the tactic, and getting it down, will definitely lift your Arena ratings. It's part of what we do, as druids.