Something so convicing it is irrefutable.
George W. Bush's argument for invading Iraq was not convincible in the slightest. My argument for poking him in the eye, however, is utterly convincible.
When one makes you believe they are a Serial Killer.
It was convincible during the conversation between Carol and Peter about how long it has been since they last seen each other. Kristi listen upon their conversation and wondered why they kept on referring to the past and that it had been a while since they killed someone and got away with it. When Kristi asked what were they talking about they took a sharp knife and duck tape and.......