(1.) Not simply the evacuation route for the common deuce but also with some "oppositional
irony" (2.) the entry point for the
male and prosthetic
penis (e.g., jelly cock) -- usually during man-on-man intercourse, and at that, when the recipient is being referred to by the other(s) as "Shirley."
The burly, hairy inmate pumped the white collar
criminal in the dirtchute -- "Take it,
Shirley," he said -- to the applause of the other inmates in the penitentiary
laundry facilities.