Mondo-Boffo Share definition Flag Mondo-Boffo is a compound word made up of two words each defined individuallly here. It means extremely-successful; very-good; best-outcome; etc. You won $10K in Lotto, Mondo-Boffo! Mondo-Boffo by JackMeough July 10, 2010 Get the Mondo-Boffo mug.