That part of a shingle, slate, or tile, which is exposed to the weather, when laid; also, one course of such shingles, slates, or tiles.
(firearms) A unit of measurement which describes how many spheres of bore diameter of a shotgun can be had from one pound of lead; 12 gauge is roughly equivalent to.75 caliber.
(slang, by extension) A shotgun (synecdoche for 12 gauge shotgun, the most common chambering for combat and hunting shotguns).