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1.
the arm visible in a picture when

someone is taking a selfie. Now Less common after the front facing camera was popularized
John: Did you see Sara's picture on Instagram?

Jim: yeah it must have been a selfie. Look at that arm!

Or.

Jim: is this a selfie?

John: I don't see a selfie arm but maybe they used their front facing camera
by Juan Pablo Montoya 69 November 03, 2013