When you take an unbelievably unique or large dump, and snap a picture using your phone to prove it to the doubters.
"You should have seen it, it stretched the length of the bowl and disappeared downwards."
Girlfriend : "Yeh....not likely"
"Here, I I send you a shelfie."
/'ʃelfi:/ (n): A photograph, usually facial, of a woman, for which the angle used in the taking has been purposefully calculated to show her bosom to best advantage.
“Dude, have you seen her Facebookpage? Since she got that boob job, her shelfie posts have gone through the ROOF!”