Chiranjeevi accepted the offers which helped him to get a Mass hero image. Chiranjeevi became a Mega star only after accepting Mass Movie offers.
Nagarjuna after got the image of a Romantic hero accepted some Mass movie offers to have the Mass Hero image. Same with Mahesh Babu, Pawan Kalyan, Junior NTR. These are all known as Mass heroes.
A Hero has mass following more than any other class. Naga chaitanya rejected some of the offers to attain a Mass Hero image.