It's a concept sweeping youtube in which a person draws eyes on their chin, covers the rest of their face (and shoulders, if they're in the frame) lies upsidedown, and then proceeds to film themselves lip-syncing to a song.

Some videos of this fad are:
youtube.com/watch?v=BUfmD6kgljk
youtube.com/watch?v=8j_z8vepBrA
OMG, did you see that new youtube channel that ONLY has chin singing videos? LOLOLOL.
by TakeMeI'mAlive! June 30, 2010
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A hilarious internet phenomenon where you draw on the basic features of a face on your chin, lie upside down, and record yourself miming a song with the camera zoomed up on your mouth. It should look like a weird, Jabba the hut-esque creature with giant lips singing.
She was chin singing again last night...
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