To die by jumping in front of an oncoming train. Comes from a combination of New York City subway code for "person under train" (12-9) and shorthand for "yourself" ("12-9 yourself"). Suggestion of how a person "ought to be killed" when one is annoyed with the other person. Similar in meaning to DIAF and DIAT. In other words: "shut up".
by New Brunswick Station (subchat) July 22, 2008

by New Brunswick Station (subchat) April 19, 2006

When underpaid transit workers attempt to get their way by not working, therefore screwing everyone working/living/playing in town
The recent transit strike made me walk across the Brooklyn Bridge!... This fucking transit strike fouled up the Green and Market-Frankford lines. Can I have a taxi, please?
by New Brunswick Station (subchat) April 18, 2006
