The Collaborative International Dictionary of English v.0.48:

bosa \bo"sa\ (b[=o]"z[.a]), n. [Ar. b[=u]za, Pers. b[=u]zah: cf.
   F. bosan.]
   A drink, used in the East. See Boza.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Boza \Bo"za\, n. [See Bosa.]
   An acidulated fermented drink of the Arabs and Egyptians,
   made from millet seed and various astringent substances;
   also, an intoxicating beverage made from hemp seed, darnel
   meal, and water. [Written also bosa, bozah, bouza.]
   [1913 Webster]