ultimum verbum 

The ultimum verbum fallacy is common among internet users who frequent message boards but is also commonly used throughout non-internet life. This fallacy, as it Latin name denotes, is simply the fallacy of having the last word. Most internet users who are keen on ruthlessly promoting their ideas will continue to post arguments or rebuttals in the face of overwhelming evidence to the contrary. Internet users who have strong opinions feel the need to have the last post as mark of external validation of their worldview. A key component of ultimum verbum fallacies on the internet is the a priori, metaphysical distinction between ITT and IRL: as if the events of ITT were not occurring in IRL. Another example of this fallacy is common in marriage. The husband, shackled down by the promise of sex, must obey his wife's commands no matter how unreasonable they may be. When she says "Honey, you can't have beer with your friends at the bar tonight!", the husband may chose to ignore that dictate but only to his peril. So in this case the wife presents an ultimum verbum case which any sharp husband would recognize as such but would not dare contest if he cares about getting laid on a somewhat regular basis.

Wife:"Honey, you can't have beer with your friends at the bar tonight!"
Husband:(under his breath) "Argumentum ultimum verbum."
Wife: "What did you say honey?"
Husband: "I said `Yes, dear!'"

"Well, I see your argument as illogical!"
"But all that I was arguing was that p implies q; r implies s. And if p or r is given, then q v s is given."
"Well I or no one else think in those terms in real life."
"Argumentum ultimum verbum."
"Well I don't see how invoking Latin like, the ancients invoked deities to support their causes, supports your case."

ultimum verbum by H.W. Eugene January 8, 2009