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15.
To have intercourse with a person in a rough, physically hurtful manner to the point where their consciousness or life is in question. An exageration of having intercourse to the point of someone dying.
I flatlined that ass so hard she was crying.
by c0d1 January 28, 2011
 
16.
Awesome paladin tank on the horde side of the Bronzebeard EU server.

"Man that Flatlíne is the shizzle"

Known for his wit, handsome good cow looks, and ability to abuse bad dps.
Omg its Flatlíne. Watch your threat before he pwns you
by angryqqer August 17, 2011
 
17.
Metal band based out of Los Angeles. Usually associated with leather clad women drinking beer and being generally slutty, kick ass chicks.
Wow, man!! We went to that Flatline show at The Whisky, and they kicked ass! I also got to go home with a hottie in a Flaline T-shirt..
by Jason January 28, 2005