Armed Boarding Vessel - Civilian ship armed and taken into the navy.
Ack Ack - Anti-aircraft (artillery).
Ack Emma - a.m. (midnight to noon).
Adrian helmet - French army standard issue steel helmet post-1916. Named after the designer.
Advanced Dressing Station : The most advanced medical post behind the Regimental Aid Post.
AEF - American Expeditionary Force.
A-frame - Inverted A-shaped wooden frame to support duckboards.
ALH - Australian Light Horse.
Alleyman : British slang for a German soldier.
Alpini - Italian Alpine troops specialising in mountain warfare.
Amiens Hut : Temporary structure of canvas on a frame used at British base camps.
Ammo-boot - Ammunition boot - British standard issue ankle boot.
ANZAC - Australian (and) New Zealand Army Corps.
AOC - Army Ordnance Corps.
AP - Medical Aid Post.
Archie - Anti-aircraft fire.
Armlet - Armband signifying special function e.g. Instructor.
ASC - Army Service Corps.
AVC - Army Veterinary Corps.
