Gage is an instrument used to measure magnitude or position; gages may be used to measure the elevation of water surface, the velocity of flowing water ...
Guage is an estimate: judge tentatively or form an estimate of (quantities or time); "I estimate this chicken to weigh three pounds"
a measuring instrument for measuring and indicating a quantity such as the thickness of wire or the amount of rain etc.
rub to a uniform size; "gauge bricks"
accepted or approved instance or example of a quantity or quality against which others are judged or measured or compared
determine the capacity, volume, or contents of by measurement and calculation; "gauge the wine barrels"
the distance between the rails of a railway or between the wheels of a train
measure precisely and against a standard; "the wire is gauged"
adapt to a specified measurement; "gauge the instruments"
the thickness of wire
mix in specific proportions; "gauge plaster"
bore: diameter of a tube or gun barrel