gauge / gāj/ (chiefly technical also gage) • n. 1. an instrument or device for measuring the magnitude, amount, or contents of something, typically with a visual display of such information. ∎ a tool for checking whether something conforms to a desired dimension. ∎ fig. a means of estimating something; a criterion or test: emigration is perhaps the best gauge of public unease.2. the thickness, size, or capacity of something, esp. as a standard measure, in particular: ∎ the diameter of a string, fiber, tube, etc.: [as adj.] a fine 0.018-inch gauge wire. ∎ [in comb.] a measure of the diameter of a gun barrel, or of its ammunition, expressed as the number of spherical pieces of shot of the same diameter as the barrel that can be made from 1 pound (454 g) of lead: [as adj.] a 12-gauge shotgun. ∎ [in comb.] the thickness of sheet metal or plastic: [as adj.] 500-gauge polyethylene. ∎ the distance between the rails of a line of railroad track: the line was laid to a gauge of 2 ft. 9 in.3. (usu. the gage) hist. Naut. the position of a sailing vessel to windward (weather gage) or leeward (lee gage) of another.• v. [tr.] 1. estimate or determine the magnitude, amount, or volume of: astronomers can gauge the star's intrinsic brightness. ∎ form a judgment or estimate of (a situation, mood, etc.): she is unable to gauge his mood.2. measure the dimensions of (an object) with a gauge: when dry, the assemblies can be gauged exactly and planed to width. ∎ [as adj.] (gauged) made in standard dimensions: gauged sets of strings.DERIVATIVES: gauge·a·ble adj.gaug·er n.