ahead of
ahead of  {prep.}
1. In a position of advantage or power over. 
He studies all the time, because he wants to stay ahead of his classmates.
2. In front of; before. 
The troop leader walked a few feet ahead of the boys.
3. Earlier than; previous to, before. 
Betty finished her test ahead of the others.
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Source: A Dictionary of American Idioms
