Bulimia nervosa is an eating disorder characterized by recurrent binge eating, usually followed by defensive vomiting.
According to the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV TR) published by the American Psychiatric Association, the criteria for diagnosing a patient with bulimia are:

-Recurrent episodes of binge eating. An episode of binge eating is characterized by both of the following:
-Eating, in a fixed period of time, an amount of food that is definitely larger than most people would eat under similar circumstances. Mainly eating binge foods.
-A lack of control over eating during the episode: a feeling that one cannot stop eating or control what or how much one is eating.
-Recurrent inappropriate compensatory behavior to prevent weight gain, such as: self-induced vomiting; misuse of laxatives, diuretics, or other medications; fasting; excessive exercise.
-Triggers include periods of stress, traumatic events, and self-evaluation of body shape and weight.
-These symptoms may occur after every meal on a daily basis or once every few months.
-The disturbance does not occur exclusively during episodes of anorexia nervosa.
Vomiting is not necessary for bulimia to be present. There are purging tupe and non-purging type of bulimia. However, induced vomiting for even few times might be a sign of bulimia.