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An immeasurable amount of something...Similar to saying "umpteen", but with more anger or frustration.
I told you for the fuckteenth time, Outlet Runner doesn't suck!
by Nirvana_Girl October 21, 2011
An indeterminate number greater than a few, but fewer than fifty.

Used to describe repetitive, boring, or pointless action.

"He has told that story fuckteen times..."
by ArloBigwater February 24, 2009
A girl exactly the age of consent.
You know Marlena? She turned fuckteen today.
by Puggles February 22, 2013