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Webster 1913 Edition

adv.

In a preventive manner.

adv.

By way of prevention; in a manner that tends to hinder.

preventively ‎(not comparable)

In a preventive way
- 2009 February 8, “Biden says U.S. ready to talk but remains prepared to act”, in Toronto Star:
  On Iran, Biden said Washington will strive to act preventively and avoid having to choose between the risks of war and the dangers of inaction.

in a preventive way