noun, noun which may take the genitive case particle 'no'
no advance reservation required; walk-in welcome
Used in signs, advertisements, or descriptions of services that do not require booking ahead of time.
このイベントは事前予約不要で参加できます。
You can join this event without an advance reservation.
事前予約不要の診療も行っています。
We also offer medical consultations that do not require an appointment.
Compound of 事前 (beforehand), 予約 (reservation), and 不要 (unnecessary).