o ‧ ver ‧ drive /ˈəʊvədraɪv $ ˈoʊvər-/ BrE AmE noun [uncountable]
1 . an additional ↑ gear which allows a car to go fast while its engine produces the least power necessary
2 . go into overdrive/be in overdrive to start being very active or working very hard:
Her career has gone into overdrive.