Mulling is when you pretend to be a member of a crowd or a group of people, or if you pretend that something belongs to you. Mulling can be both in subjective and obective ways.
"Hey sveincheese, let's mull that group of chinese people!" or "I just mulled a guy so bad Stian, took a photo and everything. But unfortunately he mullbusted me!" and "I love mulling, it's like participing in the paraolympics"