What the quincunx is
A quincunx (also called an inconjunct) is an angular separation of 150°. The signs involved share no element, modality or polarity — they have literally nothing in common — so the two planets cannot easily relate. It is a minor aspect, but a genuinely awkward one: not tense like a square, but mismatched, requiring constant small adjustments.
Where the square generates a clean conflict that can be fought, the quincunx generates a chronic sense of "this doesn’t quite fit."
How the quincunx works
A quincunx asks for ongoing adaptation. The two functions must keep making room for each other, since neither can be fully satisfied at once. Traditionally the aspect is associated with health, work and the need for adjustment; psychologically it often shows an area of life where a person feels perpetually out of sync and must improvise a working compromise.
By transit and synastry
By transit, a quincunx brings a period calling for adjustment rather than dramatic action — a nagging need to accommodate. In synastry it shows where two people find each other slightly baffling and must keep negotiating differences that never fully resolve. Use a tight orb; the quincunx is subtle.