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1. The Astro
Doing The Astro is defined as whatever you do in secret when no one's around. Everyone does The Astro.
I bet Jimmy's doing The Astro right now. He didn't come to the party.
2. The astro
1. The act of dancing without music

2. The act of dancing with no one around, with or without music
Look at that guy, he's doing the astro!
or
I bet Jack does the astro at home.