What is a male undergraduate social club called?

There isn't one single name. The term used depends heavily on the specific club's character and the university's culture. Some possibilities include:

* Fraternity: This is the most common term, especially in North America. However, fraternities often have a broader scope than just a social club, often involving philanthropy, academics, and other activities.

* Social Club: A simple and straightforward term that applies if the club's primary focus is socializing.

* Gentlemen's Club: A more formal and less common term, possibly implying a more exclusive nature.

* The club may simply have a name that doesn't explicitly indicate its gender or purpose (e.g., "The Phoenix Club," "The Sigma Society").

The best term to use will depend on the context.