1. A designator which indicates the order in which a number of messages shall be served. Four precedence levels are provided for SDS, with one being the highest and four the lowest. Messages with precedence level one are served first and those with level four last. These correspond to the four precedence levels, Flash, Immediate, Priority, and Routine respectively. 2. (Reconnaissance) A letter designation, assigned by a unit requesting several reconnaissance missions, to indicate the relative order of importance, within an established priority, of the mission requested.