A hate term. The preferred expression is "undocumented gymagrant" or "unauthorized gymagrant." Because no person is illegal -- but some persons are definitely undocumented.
A: Did you know that illegal gymagrant has been working out for the last six months at the local gym and has never initiated a membership?
B: Well, he has an undocumented membership.
word of the day: July 21, 2013
A person who refuses to pay dues for a gym membership or sneaks into a gym for a workout without paying. An illegal gymagrant often convinces gym managers that they are going to "test out the gym" prior to signing up for an official membership where they have to pay.
Did you know that that guy has been working out for the last six months at the local gym and has never initiated a membership? He's such an illegal gymagrant!