For the first time; indicates doing or experiencing something for the first time (used as an adverb).
初めて日本に来たとき、寿司を食べました。
When I came to Japan for the first time, I ate sushi.
初めて彼に会ったのは大学の入学式だった。
The first time I met him was at the university entrance ceremony.
初めて聞いたときはとても驚いた。
I was very surprised when I heard it for the first time.
Grammar: used after the -te form of a verb (Vて初めて) meaning 'only after doing ... does ... happen/does one realize ...'.
親になって初めて子育ての大変さが分かった。
Only after becoming a parent did I understand how hard raising a child is.
問題を解決して初めて安心できる。
Only after solving the problem can I feel relieved.
日本語を勉強して初めて、日本の文化が少し理解できるようになった。
Only after studying Japanese did I begin to understand Japanese culture a little.
As a noun: the first time/an initial experience; colloquially used to refer to someone's 'first'.
映画を見たのはこれが初めてだ。
This is the first time I've seen that movie.
彼女にとっての初めては特別な思い出だ。
Her 'first' is a special memory for her.