Comical corruption of "fuckin' tremendous!". Used for fun, or when use of the actual phrase out loud would be inappropriate.
"You missed last night's piss-up, man! Oh, meckin' tre-FUN-dous!!!"
or
"Whoa, your new girlfriend has one meckin' trefundous ass, dude."
or
"Whoa, your new girlfriend has one meckin' trefundous ass, dude."
by Uncle Al, the Perv's Pal July 29, 2005