A set meal (usually a main dish with side dishes, rice, and soup); a fixed menu often served at cafeterias and restaurants.
ランチは定食にします。今日は焼き魚定食です。
I'll have the set meal for lunch. Today it's the grilled fish set.
その定食には小鉢と漬物が付いてきた。
That set meal came with a small side dish and pickles.
学生街の食堂は定食が安くて人気だ。
The cafeteria in the student district is popular because its set meals are cheap.