a restaurant that mainly serves set meals (teishoku) — a main dish with side dishes, rice, and miso soup.
会社の近くに安くてうまい定食屋がある。
There is a cheap and tasty teishoku restaurant near the office.
今日は定食屋で魚の定食を頼んだ。
Today I ordered a fish set meal at a teishoku restaurant.
昼は定食屋が混むので、少し早めに行ったほうがいい。
Teishoku restaurants get crowded at lunchtime, so it's better to go a bit early.