noun, noun which may take the genitive case particle 'no'
oldest member; longest-serving member
Refers to the person who has been in a group, organization, or team the longest. Often used in workplace or military contexts.
He is the longest-serving member of this department.
As the oldest member of the company, he knows its history well.
Compound of 最 (most) + 古参 (seniority, long service).