This symbol is the Japanese character "DÒ" (pronounced doe). "DÒ" refers to practice as a way of life. The closest (and rarely used) word in the English language for one who lives according to this principle is "practic." The definition of practic is "a person concerned with action or practice, as opposed to one concerned with theory."
A young female rioter famously told a BBC cameraman at the time "we want to show what we can do", which is of course a euphemism for 'look at us!'. The message was clear - we'd made Britain's teenagers feel undervalued for far too long and now we were in the midst of their collective temper tantrum.