Eid Mubarak (عيد مبارك)
Means ‘Happy Eid’. Eid is the Muslim celebration that happens when the month of fasting, Ramadhan, ends and also when the pilgrims have completed their pilgrimage in Mekkah.
The translation above is innacurate but gives the general intention of the phrase. Literally translated it would be ‘(Have a) blessed Celebration’. If someone says Eid Mubarak to you it is customary to reply back with Eid Mubarak as well.