1. a personification of the federal government or citizens of the US, typically portrayed as a tall, thin, bearded man wearing a suit of red, white, and blue.
Word Originearly 19th century: said (from the time of the first recorded instances) to have arisen as an expansion of the letters US.
Personification of the United States of America and its government
Uncle Sam is a common national personification of the federal government of the United States or the country in general. Since the early 19th century, Uncle Sam has been a popular ... Wikipedia