Illegal Gymigrant 

A term describing a person who sneaks into the gym without paying, or someone who uses another's gym pass in order to work out.

Brad always worked out three times a week, but, being an illegal gymigrant, he never actually paid to use the gym facilities - he just snuck past the front desk.

Illegal Gymigrant by L0 June 13, 2010

Illegal Gymagrant 

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!

Illegal Gymagrant by TCB451 July 16, 2013

Illegal Gymagrant 

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.

Illegal Gymagrant by FlaviusP August 20, 2013