When you are at your place of employment and are assaulted by a hoarde of (or a) ninja(s) this is referred to as an On The JobNinjury.
Doug: "Where's Fred today? I didn't see him in his newly bloodstained cubicle!"
Ernest: "That bastard was attacked by ninja's yesterday, hence the blood stains."
Doug: "being a victim of an On The Job Ninjury is awful. this has been a Public Service Announcement..."
1. The act of behaving like a ninja.
2. Thievery.
3. (less frequently) Any act of skulduggery.
1. With these new darkvision goggles I got in the mail, I can see the darkies sneaking around near the park. Their ninjary will get them nowhere!
2. The old lady isn't watching her purse, so quit being a pussy bitch and show me your ninjary skills.