This is a feature that some fire inspectors require on some doors. (Fire codes are still largely a local matter, though standardization is becoming the trend.) This means that a user must make only one motion in order to open a door to exit. For example, a door which is designated for single motion egress cannot have both a latching doorknob and a separate deadbolt, since that requires the user to perform two distinct actions to open the door. There are products designed for properly securing doors that require single-motion egress. A professional locksmith can make sure you comply with local codes while still protecting your property!