A cannon is any large tubular firearm designed to fire a heavy projectile over a considerable distance. The term can apply to a modern day rifled machine gun with a calibre of 20 mm or more (see autocannon).
Cannon also refers to a large, smooth-bored, muzzle-loading gun used before the advent of breech-loading, rifled guns firing explosive shells. Although a variety of such guns are commonly referred to as "cannon", the term specifically refers to a gun designed to fire a 42 lb shot as opposed to a "Demi-cannon" (32 lb), Culverin (18 lb) or Demi-culverin (9 lb). "Cannon" derives from the Latin canna—a tube. Bombard was earlier used for "cannon", but from the early 15th century came to refer only to the largest weapons. "Cannon" serves both as the singular and plural of the noun.<ref>Wikipedia page on Cannon</ref>
Relation to LG15
Fans often confuse the word cannon with the highly relevant term canon.