little black book

Noun

An address book, especially one in which the details of one's lovers are recorded

Japanese Meaning

特に恋人の連絡先や情報を記録した私的なアドレス帳 / 恋人の詳細が記録された小型の私的名簿

She flipped through her little black book, smiling at the names she hadn't called in years.

彼女は恋人たちの連絡先が書かれた手帳をめくり、何年も電話をかけていない名前に微笑んだ。

Sense（1）

An address book, especially one in which the details of one's lovers are recorded

little black books

（ plural ）