in public; public occasion; public setting
Refers to a situation or place where one is in front of an audience or the general public. Often used in formal contexts.
Speaking in public makes me nervous.
The issue was discussed in a public forum.
Compound of 公開 (public, open to the public) + の (possessive particle) + 席 (seat, occasion). Literally 'a seat of public openness', used idiomatically to mean a public occasion or setting.