A bulimic has powerful urges to overeat: they regularly binge-eat and feel out of control as theydo so. They then try to undo the effects of the bingeing by purging (usually by making themselves sick or taking laxatives) or by compensating (fasting and excessive exercising). They are extremely worried about gaining weight.
It's impossible to estimate how widespread this kind of disordered eating is, since feelings of shame often prevent people from seeking help. Bulimia and bingeing have traditionally been seen as female problems but increasing numbers of men and boys are now affected as men become more body-aware. In order to be diagnosed as clinically bulimic a person would need to binge and purge/compensate at least twice a week over a minimum of three months. However, anyone who is stuck in the binge and purge/compensation cycle, regardless of whether it matches the clinical criteria for bulimia, needs to address that problem. So if you feel your eating patterns are disordered, it's a good idea to talk to a counsellor.
It's not easy to define a binge-eating episode. Some people consider a second bowl of cereal to be out of control eating. Others will eat enormous amounts of food and be almost unable to move afterwards. Secrecy, shame, anxiety and feeling out of control are all shared feelings. People often report feeling almost in a trance during bingeing, followed by a sense of relief and cleansing if they make themselves sick. The behaviour is highly addictive. Counselling can help you to break the binge purge/compensate cycle. It can also help you look for less destructive ways to reduce anxiety and investigate the roots of your emotional difficulties.