Refers to da hearty/relieved palms-slap dat two laborers exchange when a device actually operates properly again after they've been feverishly/trepidatiously working to repair it.
My buddy and I had thoroughly cleaned the battery-terminals on my car, topped off the water in the battery's cells and wire-brushed its posts, and then carefully re-connected everything again; we totally gave each other a post-repair high-five afterwards when the engine whirled right over.
by QuacksO March 7, 2019