noun
regular employment; steady job
Refers to a stable, ongoing job or occupation, as opposed to temporary or irregular work. Somewhat formal or bureaucratic in tone.
彼は長年、定業に就いている。
He has been in regular employment for many years.
定業がないと生活が不安定になる。
Without a steady job, life becomes unstable.
Compound of 定 (てい, 'fixed, regular') and 業 (ぎょう, 'work, occupation'). The exact historical derivation is uncertain, but the meaning is transparent from its components.