동기가 · 동기를
classmate (same year), peer who started at the same time
Example
대학교 동기들과 지금도 자주 만나요.
I still often meet my college classmates.
Word parts
동 same+기 period
Literally 'same period' — people who entered school or a company together.
Good to know
Homonym warning: 동기 (動機) also means 'motive'.