Verb. triple dog dare. (slang, US) Used to denote compounding levels of dare”seriousness”; the escalation of a double dog dare. I triple dog dare you to jump.
To “double dog dare” someone is to challenge them emphatically or defiantly, although the “challenge” is often meant humorously, or at least not very seriously: “I double dog dare you to eat the entire box of doughnuts!”