noun
seniority system; seniority-based promotion system
Refers to the traditional Japanese employment system where promotion and pay are based on age and length of service rather than merit.
日本の大企業では、まだ年功序列制度が残っているところが多い。
In many large Japanese companies, the seniority system still remains.
年功序列 is a shorter form often used in conversation; 年功序列制度 explicitly refers to the system as a whole.
Compound of 年功 (years of service) + 序列 (order, ranking) + 制度 (system).