The Wheel of Fortune is about Luck, about transitions and changes, sometimes about Karma. Generally speaking, it is about things that happen to us that change our lives...rather than, as with so many other cards, things we ourselves do to create a change. What does it mean reversed?
1) Opposite: Usually the Wheel is read positively as moving up. There is luck and good fortune in it, the implication that we are going to be moving up (deservingly) while someone else (deservingly) moves down. Thus, the opposite would be, quite simply, bad luck, misfortune. Instead of heading up to the top of the wheel, we're going to be hitting the bottom. It's the nadir instead of the zenith. Someone else will be getting the promotion or position we want, and we, alas, might well be getting laid off or transferred.
As with good luck, there is nothing to be done about bad luck but accept it and make the best out of it.
2) Blocked: If we read the energy as blocked, then we have to assume that the wheel wants to move up, wants to turn, but isn't being allowed to. Hence, in this reading, the wheel is stuck. It is moving neither up nor down. Rather like a when a Ferris Wheel comes to a stop, wherever you are, there you are and there is no change.
I, personally, find this more distressing than if the wheel were moving down. An unmoving wheel means no changes - no going anywhere. The problem is, that the querent might not be able to alter this as the Wheel's energy usually comes from without - so if the company that a person works for is freezing all jobs, no promotions or demotions, then that's the way it is and there's nothing the employee can do to change that. They can leave the job, but they can't force the company to "unfreeze" and start promoting/demoting again.
3) Upside-down: There seems, on the surface, little difference if we turn this card upside-down - it's a wheel, a circle, with no top, no bottom. And yet, using Rider-Waite, we can see a change. The Sphinx is at the bottom. The "Set" creature (chaotic/devilish creature) is at the top. The Serpent switches sides and is moving up instead of down.
To understand, think of it this way. The Sphinx is at the top, hovering above the Ferris wheel. You ride up to talk to the Sphinx. Then you ride down and have to deal with Set. Then back up again.
Reverse the card and the implication is that when you rise to the top, you meet Set instead of the Sphinx! What ought to be good luck is going to be bad. In this case, the promotion that should give you what you want, that ought to be good fortune, lands you in hell instead.
This is a bit worse than just "bad luck." The idea here is that the external forces creating that luck are unreliable; you can't trust the luck you're getting to be what it seems.
Curious about this card when upright? Go to our Tarot Card Meanings.