Fill or Kill is a type of order that requires that all of the securities in the order be purchased or sold immediately or not at all.
Applying "Fill or Kill" to Securities Exams:
Investors who are trying to establish a position simultaneously in multiple securities may need to do so immediately when certain market conditions exist for the securities. As such if an investor is looking to purchase 1000 shares of XYZ at 40 to offset the execution of orders in derivatives or other securities the investor may enter th order as a Fill or Kill order. The order would have to be executed immediately for all 1000 shares at 40 when presented to the market or the entire order in canceled.