「初めて」 means 'for the first time'. It indicates that an action or experience is entirely new and has never occurred before. It emphasizes the novelty of the event or situation being encountered.

今まで(いままで)一度(いちど)も経験(けいけん)したことがない、最初(さいしょ)の出来事(できごと)を表(あらわ)します。