Arrangement of five petals or leaves, of which two are exterior, two interior, and the fifth partly exterior, partly interior.
- A dictionary of scientific terms. By Henderson, I. F.; Henderson, W. D. Published 1920. (noun) (n.) (noun)
A plantation of trees disposed in a square, consisting of five trees, with one at each corner and one in the middle.
- Nuttall's Standard dictionary of the English language. By Nuttall, P.Austin. Published 1914. (noun) (n.) (noun)
An arrangement of five objects in a square, one at each corner, and one in the middle; in bot., the arrangement of the leaves of a bud into five, of which two are exterior, two interior, and the fifth covers the interior with one margin, and has its other margin covered by the exterior.
- Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874. (noun) (n.) (noun)

Usage examples:

It was a fine old house, roomy, airy, bright, sunny, cheerful, with large apartments and a capital play- ground, formed by that old- fashioned device, a quincunx of linden trees, under whose shade we carried on very Amazonian exercises, fighting having become one of our favorite recreations.
- Records of a Girlhood by Frances Ann Kemble
And, instead of the road, with the Gloucestershire hills and lessening clouds in perspective, have we not the cedar quincunx
- Anna St. Ives by Thomas Holcroft
To this ambition, perhaps, we owe the Frogs of Homer; the Gnat and the Bees of Virgil; the Butterfly of Spenser; the Shadow of Wowerus; and the Quincunx of Browne.
- Curiosities of Literature, Vol. 1 (of 3) by Isaac D'Israeli