(1) In a goal-programming problem, a statement that stipulates the ordering of the goals, so that a solution that satisfies the priority k goal is always to be preferred to solutions that satisfy the lower priority goals k + 1,....  Goal programming. (2) In queueing theory, this means that an arriving higher priority item pushes a lower one out of service because the newcomer has higher priority. Service of the preempted customer can either continue from the point of its interruption or totally start anew.  Queueing theory.