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1.
What occurs when two objects move very fast in the same direction at the same speed very close together.

Generally refers to motor vehicles, but can be used to describe similar action by any other object as long as it's moving fast enough.

"Baby Action" itself refers to the fact that if two vehicles were to Baby Action in an action movie, the small children inside (who the drivers/passengers are fighting over) could get out and up onto the roofs of the vehicles and fight kung-fu style.

The maximum distance between vehicles for Baby Action to occur is about 6 feet, and the minimum speed is 50 miles per hour. However, if the vehicles inoilved cannot reach the minimum speed for Baby Action, the maximum possible speed for that particular vehicle is declared to be the maximum.
"Look, those two street punks are drag racing! I think I see Baby Action!"
by Erca 'Kuzudee June 24, 2005