Although the source is personally repugnant to me, here is one definition of "small arms" from the United Nations Development Program:
[b]Small Arms[/b]
Revolvers and self-loading pistols
Assault rifles, rifles and carbines
Sub-machine-guns and light machine-guns
[b]Light Weapons[/b]
Heavy machine-guns
Hand-held and mounted grenade launchers
Portable anti-aircraft guns
Portable anti-tank guns, recoilless rifles
Portable launchers of anti-tank and anti-aircraft missile systems
Mortars of calibres of less than 100 mm
[b]Ammunition & Explosives[/b]
Cartridges (rounds) for small arms
Shells and missiles for light weapons
Mobile containers with missiles or shells for single-action anti-aircraft and anti-tank systems
Anti-personnel and anti-tank hand grenades
Landmines and Explosives
[url]www.undp.org/erd/archives/brochures/small_arms/sa8.htm[/url]