(in the manual of arms in close-order drill) a position in which the rifle is held at the right side, with its butt on the ground.
(as an interjection) the command to move the rifle to this position.
Origin of order arms
First recorded in 1835–45
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for order arms
military the order in drill to hold the rifle close to the right side with the butt resting on the ground
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012