Cinco De Mayo Definition

sēngkō də mäyō

noun

May 5, anniversary of the victory of Mexico over French forces at Puebla in 1862: observed by Mexicans and Mexican Americans.

Webster's New World

pronoun

A national celebration in Mexico, commemorating the victory of Mexican forces led by General Ignacio Zaragoza over the French expeditionary forces in the Battle of Puebla on May 5, 1862, also celebrated widely by immigrants living in the United States.

Wiktionary

Origin of Cinco De Mayo

Spanish, from cinco (“five") + de (“of") + mayo (“May"); May fifth

From Wiktionary
Spanish cinco five de of Mayo May

From American Heritage Dictionary of the English Language, 5th Edition