[AusRace] What is a RIG?

[Mike McBain]

Ausracers

I think I caught a callers comment yesterday that one of the 
winner's, and it may have been Headhunter, was a rig and he mentioned 
that is was unusual?

I was going to ask you all "What is a rig please?" but decided to 
Google first and so for those who may not know....it's a gelding one 
of whose testicles has not descended and they have or can become a sire!

Is this correct?

Mike.