Meaning of “gauge” - Learner’s Dictionary

gauge

noun [ C ] us uk /ɡeɪdʒ/
JUDGING

a way of judging something such as a situation or what someone thinks or feels:

Street interviews aren't an accurate gauge of public opinion.
MEASURING

a method or piece of equipment that you use to measure something:

a fuel gauge

(Definition of “gauge noun” from the Cambridge Learner’s Dictionary © Cambridge University Press)