JA - (Country Code) Japan.
JCS - Joint Chiefs of Staff.
JE - (Country Code) Jersey.
j.g. - junior grade.
JM - (Country Code) Jamaica.
JO - 1. (Country Code) Jordan. 2. (Obsolete) Junior (FS) Officer
JQ - (Country Code) Johnston Atoll.
JTX - joint training exercise.
JU - (Country Code) Juan De Nova Island.
JUMPS - Joint Uniform Military Pay System.
junior officer - 1. U.S. Navy or Coast Guard officer in the rank of either ensign, lieutenent junior grade (j.g.), lieutenant, or lieutenant commander. Equivalent to U.S. Army, Air Force, or Marine company grade officer plus the rank of major. 2. (Obsolete) U.S. Foreign Service generalist in the grade of either FS-06, FS-05, or FS-04. See instead: ELO.