| a part of an army or military force detached from the main body to bring up and guard the rear from surprise attack, esp. in a retreat. |

| rear guard n. A detachment of troops that protects the rear of a military force. [Middle English reregarde, from Old French : rere, backward (from Latin retrō; see re- in Indo-European roots) + guarde, guard (from guarder, to defend; see guard).] |