The Collaborative International Dictionary of English v.0.48:

Bairam \Bai*ram"\, n. [Turk. ba["i]r[=a]m.]
   Either of two Mohammedan festivals, of which one (the Lesser
   Bairam) is held at the close of the fast called Ramadan, and
   the other (the Greater Bairam) seventy days after the fast.
   [Webster 1913 Suppl.]