CANNON, a gun or piece of ordnance. The word, first found about 1400 (there is an indenture of Henry IV. 1407 referring to canons, seu instruments Anglice gunnes vocata), has been commonly applied to any form of firearm fired from a carriage or fixed mounting, in contradistinction to "small-arms," which are fired without a rest or support. An exception must be made, how ever, in the case of machine guns (q.v.), and the word as used in modern times may be defined as follows : "a piece of ordnance mounted upon a fixed or movable carriage and firing a projectile of greater calibre than 12in." In French, however, the term canon has been applied to the barrel of small arms, and also, as an alter native, to mitrailleuse or mdtrailleur, to machine guns, as well as to ordnance properly so-called. For details see ARTILLERY, GUN, ORDNANCE, SMALL ARMS, etc. For "cannon" in billiards see