May Day

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun May 1, observed in the United States, Canada, and parts of Western Europe in celebration of the coming of spring.
• noun May 1, observed as a holiday especially in socialist countries in honor of labor and labor organizations.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The first day of May, the traditional day for pagan fertility rites.
• noun The first day of May, a spring festival, a celebration of the beginning of the spring.
• noun The first day of May, a world-wide workers' holiday.