Webster's Revised Unabridged Dictionary · 1913

Cid

Cid , noun

[Sp., from Arabic seid lord.]

1.
Chief or commander; in Spanish literature, a title of Ruy Diaz, Count of Bivar, a champion of Christianity and of the old Spanish royalty, in the 11th century.
2.
An epic poem, which celebrates the exploits of the Spanish national hero, Ruy Diaz.