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The moment where everyone in the car starts singing along to the song on the radio, CD player or iPod. Usually caused by long periods of boredom during highway trips.

This phenomenon usually ends up in a long streak of musical numbers where everyone belts out songs they know, usually if controlled via iPod.
The trip was relaxing until Bohemian Rhapsody started playing and it turned into a fucking Highway Musical.
by DannyLion July 09, 2011
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