Here I read this:
Could someone explain what is the meaning of the bold expression?
The meaning of "on steroids" is: In a very large, enhanced, or exaggerated form.
I assume that you know what "object" means, but just to make sure: A structure that combines data and the procedures necessary to operate on that data.
Additionally, as noted below in the comments, the term
Map object, which is a different and more powerful type of object than an
Object object. As is explained in the documentation, here.
So in this context, it more specifically means that a Map (object) is like a very powerful and enhanced Object (object).