remembrance / mention / reminder
Masculine verbal noun (maṣdar) of ذَكَرَ. Also refers to the Quran itself (الذِّكْر = the Reminder). Related: تَذْكِيرٌ (reminding), مُذَكِّرٌ (reminder/one who reminds).
Dhikr encompasses all forms of remembering God: reciting the Quran, repeating His names, supplication, and contemplation. Sufi traditions especially emphasize dhikr circles.