社会人 (shakaijin) means “working adult”

More examples

社会人になると、学生のころとは違う責任を感じます。sha kai jin ni na ru to gaku sei no ko ro to wa chiga u seki nin o kan ji ma su

When you become a working adult, you begin to feel a different kind of responsibility from when you were a student.

Refers to someone who is part of adult working life rather than a student.

サラリーマンsararīman: A salaried employee, especially one working for a company.
会社員kaishain: A person employed by a company or corporation.

社会に出て職業を持ち、働いている成人。sha kai ni de te shoku gyō o mo chi hatara i te i ru sei jin

The compound 社会人 (shakaijin) consists of 社会 (shakai, "society") and 人 (jin, "person"), expressing membership in society through work.

The Japanese word 社会人 (shakaijin) does not mean a sociable person; it usually refers to someone in working life.