Answer:
it is an adverb
Gauge is a noun or a verb.
verb - to measure accurately the size of something using a gauge, to estimate the size of something.
Can you gauge the size of the crowd here today?
noun - a device for measuring the size of something, a standard measure or scale of measurement, the thickness of sheet metal or wire.
Use the pressure gauge and check the tires. I have some 10 gauge wire that we can use.