To lose any/ all control of bowels, especially to defecate on floor.
Can also mean to do something bad and then hang around a few hours, not helpping clean up.
(This term is in common usage at Southridge, in Beaverton, OR)
"Ohhh he just T-Shapped" on the floor!"
"Yeah dude I i puked on the mirror and broke the desk, then i T-Shapped for a while."