The Quincunx is a geometric aspect between two planets that are at roughly 150 degrees apart (give or take an orb of a few degrees). This aspect indicates an irritating energy that makes it very difficult for the two planetary energies to work effectively with each other, as if they were speaking different languages. The annoying nature of the energy may not be easily understood. As a result, it becomes important to be very flexible and adaptable. It helps to increase your awareness of what is happening and be willing to think "outside the box."
In a natal chart the person often develops a greater appreciation for the intricacies and complexities of life where the two planets are involved, as opposed to seeing life in all-or-nothing, polarized terms. On the other hand, the ability to see the subtleties and shades of grey can also make it difficult to make a clear decision.
Planets in quincunx are typically five signs apart. This means the two signs where the planets reside have no qualities in common. Similar to the semi-sextile, they have different and incompatible elements, different modalities and different polarities. In the case of an out-of-sign aspect, it may soften the irritation somewhat, since it would involve signs that are either trine or opposed to each other, giving them a bit of common ground. On the other hand, this might also muddy the cooperative energy of the trine or the balanced energy of the opposition.