The goal of a dictionary is to be a reliable indicator of actual usage, so an authoritative dictionary is a bit of a contradiction. Almost all English linguists reject that sort of prescriptivism.
Meaning that the opinion of the experts is that a word's "true meaning" is however it is commonly understood by the people using it.
According to dictionary.com[0], that's exactly what it means.
Introvert - noun - A shy person.
[0] https://www.dictionary.com/browse/introvert