quincunx: (n.) an arrangement of five things in a square or rectangle with one at each corner and one in the middle

I used this word in casual conversation at a bar on Friday night. I ran into a friend of my buddy Martin’s, who was there with two friends of her own. Martin not being present, the four of us started talking, and she mentioned that her two comrades also knew Martin, and that we formed some sort of trapezoid of some kind. I had to strike while the iron was hot.