Abbreviation of 'Jack the Ripper'. Used to describe someone who is deemed to be psychotic and/or murderous.
Guy 1: You seen that guy down the park who carries a knife with him?
Guy 2: Yeh, he threatened to kill me because I accidently kicked a football at him. He's a real JTR...
a girl who only cares about this one boy and who is obsessed with him but won’t date him. she also hates on josh allen for no reason like really!?! she’s always like he’s so ugly LIKE WHATTT HES SO HOT
boy- have you seen carlena!?!
girl- yeah she hated on josh allen for no reason