When speaking of Zbrush, a "blocking" is like a first volume preview. i.e. you do a set up of the elements in basic forms without detail to know if they work with each other over a mannequin.
Nothing is really finished, just an approximation to their volumes. You can even do it just with spheres and boxes. In my case, I went a bit far away and did the basic forms of a uniform over my female mannequin.
This was one of my Zbrush studies practices. This character was going to be at the end my final practice's character, that should be completely modeled, posed, painted and rendered.
Hope you like this starting point.