The belief that God is dead, or in other words, that religion is dying off. This was coined around the moment in time in which humanity was awakened to the idea that a theistic God may not exist.
(In Greek, Theos means God and Thanatos means death.)
A religion, such as Christianity, that is practiced every holy day, involving all Halo 3 Xbox Livesubscribers. Holy Days are every night, from 6:00 PM-6:00 AM.
Person A: I celebrate Christianity, therefore my favorite day is December 25th.
Person B: Well I celebrate Halo Threetianity, and our holiday is September 25th.
A portmanteau of "threating" and "romantic" from an episode of "Fairly Odd Parents" wherein Timmy Turner's parents try to help Timmy write an effective love-email to his crush Trixie Tang by combining the usual lovey-dovey cliches with threatening that she'd better date him if she ever wants to see her parents again.