Nine

[Sarah]

Eight and one more; one less than ten; as, nine miles. Ninemen's morris. See Morris.-- Nine points circle (Geom.), a circle so related to any giventriangle as to pass through the three points in which theperpendiculars from the angles of the triangle upon the oppositesides (or the sides produced) meet the sides. It also passes throughthe three middle points of the sides of the triangle and through thethree middle points of those parts of the perpendiculars that arebetween their common point of meeting and the angles of the triangle.The circle is hence called the nine points or six points circle.

[Sarah]

Not the definition of the girth of the barrel, but rather it's bore - the width of the hole that goes through the barrel. Also, not coincidentally, the diameter of the bullet - 9mm.

Refers to a pistol, usually a semi-automatic, ostensibly a 9mm.

Aside: The U.S. Army's standard pistol is a 9mm semi-automatic.

[Sarah]

A 9mm handgun

[Sarah]

A firearm, usually a semi-automatic pistol, chambered for the 9x19mm parabellum cartridge.

[Sarah]

A semi-automatic handgun designed to fire cartridges in caliber 9mm Parabellum, aka: 9mm Luger, 9x19 NATO.