I'm a middle-aged person who is not up on the latest trends and am not a social media user. But a few days ago on CNN, the anchors were going on about the latest celebrity "selfie" that had "gone viral." My first thought, of course, was "why in the #%%^ is this news?" but then I looked at the photo they were showing. One could see both ofthat the subject's handssubject was not holding a phone or camera, and the photo was clearly taken at a distance of 20 or so feet. In other words, it was not taken by the subject. Shouldn't that have made it a "someone-elsie?" Or better yet, a plain old-fashion "photograph?"
On the other hand, the celeb had posted the pic to his own something-or-other (maybe insta-gram) account. So is that what made it a selfie?
I read this and this. Each seems to indicate a selfie is taken by the subject, but neither is perfectly clear.
By the way, if this is not the proper forum for asking about slang, let me know in the comments and I will gladly delete.