flatliner
noun
1
a dead person; a dead thing. From FLATLINE (to die). Flatliners is a 1990 film by Joel Schumacher in which five medical students experiment with the line between life and death US, 1998.
2
a mobile phone user who allows the phone's batteries to run down. A Manchester youth usage, from the sense 'a dead person', possibly, here, specificially 'brain dead' UK, 2003.
3
in poker, an unskilled and uninspired player. The moral equivalent of 'brain dead' US, 1996.
4
4-methylthioamphetamine, the recreational drug best known as 4-MTA UK, 2004