Muslim missionary involved in da'wah. It can also have a general meaning reffering to someone who calls others to a certain belief.
Da'wah
inviting others to Islam. Missionary work.
Daff
tambourine used in Arabia.
Dhikr
remembrance for the sake of Allah.
Dhimmi
a non-Muslim living under the protection of a Muslim state. He is exempt from duties of Islam like military and zakat but must instead pay a tax called jizyah.
Dhu-n Nurayn
it means 'Possessor of the Two Lights'. It is used to refer to Uthman ibn Affan because he married two of the Prophet's daughters.