The accidental (or possibly masochistic) act of 'zipping yourself.' The zip job is generally the collision of a desperately needed bathroom break and being in a hurry to get somewhere. The perfect storm...
The zip job is identified by a short period of confusion, followed by a flash of insight and intense pain/swearing.
"I gave myself a zip job last night."
"OMG, are you okay?"
"Yeah, actually I kinda liked it."
a zip job is a hand job through the pants
ex: "she just gave me a sick zip job under the table at thanksgiving, I sure was thankful!"