: a measurement (as of linear dimension) according to some standard or system: such as
(1)
: the distance between the rails of a railroad
(2)
: the size of a shotgun barrel's inner diameter nominally expressed as the number of lead balls each just fitting that diameter required to make a pound
a 12-gauge shotgun
(3)
: the thickness of a thin material (such as sheet metal or plastic film)
(4)
: the diameter of a slender object (such as wire or a hypodermic needle)
(5)
: the fineness of a knitted fabric expressed by the number of loops per unit width