noun. Tweet. : a holiday celebrating the anniversary of a country's independence from another country that ruled it in the past; especially: July 4 celebrated as a legal holiday in the U.S. in honor of the day when the Declaration of Independence was signed in 1776.oun. Tweet. : a holiday celebrating the anniversary of a country's independence from another country that ruled it in the past; especially: July 4 celebrated as a legal holiday in the U.S. in honor of the day when the Declaration of Independence was signed in 1776.