|1.||somebody else's problem|
(n.) a device which allows you to render an object invisible if no one expects it to be there, as seen in the Hitchhiker's Guide to the Galaxy
"An SEP," he said, "is something that we can't see, or don't see, or our brain doesn't let us see, because we think that it's somebody else's problem. That's what SEP means. Somebody Else's Problem. The brain just edits it out, it's like a blind spot. If you look at it directly you won't see it unless you know precisely what it is. Your only hope is to catch it by surprise out of the corner of your eye."