higher rank than that of others especially by reason of longer service
"The team leader was promoted because her seniority in the department gave her a clear advantage over the newer hires."
A measure of the amount of time a person has been a member of an organization, as compared to other members, and with an eye towards awarding privileges to those who have been members longer.
"The manager decided that only employees with enough seniority could request remote work on Fridays."