A nickname for "The Pennsylvania Railroad," a Class I American railroad that was established in 1846 and headquartered in Philadelphia, Pennsylvania. It was the largest railroad in the United States until the second half of the 20th century. Every man in my family worked on or for the Pennsy from the time it was founded up until it merged with New York Central in 1968. I have fond memories of riding along the Pennsy to visit my grandparents when I was a kid.
See also: Pennsy
n. Pennsylvania. I went to a conference in Pennsy last year.