Āsāḷha Pūjā, Festival held in Theravāda countries to commemorate the Buddha's first sermon in the Deer Park. The festival takes its name from the fact that the sermon was thought to have been delivered on the full moon night of the month of Āsāḷha. In Sri Lanka the festival is known as the Esala Perahera.

A Dictionary of Buddhism, Oxford University Press, 2003, 2004 (which is available in electronic version from answer.com)