jello Share definition Flag Mediocre sex - comes from the saying "Sex is like jello. When it's good, it's really good. But when it's bad, it's still pretty good." A: "So, you shagged her last night? How was it?" B: "Jello." A: "Beats watching TV, right?" jello by Prp Guy April 23, 2006 0 0 Get merch Get the jello mug. Buy Now — $32.95 See more merch