If you are not familiar with that one, it’s when you do exactly what the other person does.
In the training world, this means just replicating the exact exercise you see another trainer doing and continuing to do so for the entire session.
They take a lackadaisical approach to training and don’t even attempt to prepare beforehand what type of routine they are going to put their clients through.
I remember some of the lazier trainers playing “repeater” with me on some occasions.
If you have picked up a weight at some point in your life, then you have some knowledge to share with a client, no matter how horrible your technique may be.