Yes, it means to think prayerfully about a specific mystery of the Rosary.
Simply put, it could involve taking the Holy Scripture, such as the Gospel. For example, in the Annunciation mystery, you would read it carefully and thoughtfully. Then, after reading the next passage, meditating means reflecting on it, praying attentively in the presence of God, and being fully aware.
This is the method of meditation or reflection on the mysteries of the Rosary through the Holy Scripture.