O gauge

[ oh ]
/ oʊ /

noun

a model-railroad gauge of 1.25 inches (32 mm).
Also called Q gauge. a model-railroad gauge of 1.1875 inches (30 mm).

Origin of O gauge

First recorded in 1900–05
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019