Goose is a gander Share definition Flag Surprising someone with a thumb up the butthole when they're not looking, while exclaiming, "goose is a gander!" Tiffany: "What the hell are you doing back there?" Nora: "Goose is a gander!" Goose is a gander by norandtiff January 26, 2011 Get the Goose is a gander mug.