a mausoleum at Agra in northern India built by the Mogul emperor Shah Jahan (1592–1666) in memory of his favourite wife, completed circa 1649. Set in formal gardens, the domed building in white marble is reflected in a pool flanked by cypresses.
perhaps a corruption of Persian Mumtaz Mahal, from mumtāz 'chosen one' (the title of the wife of Shah Jahan) and mahal
Taj Mahal in other Oxford dictionaries
Definition of Taj Mahal in the US English dictionary