Wiktionary
n. A movement that promotes anorexia nervosa as an acceptable lifestyle choice.
Wikipedia
Pro-ana refers to the promotion of behaviors related to the eating disorder anorexia nervosa. It is often referred to simply as ana and is sometimes personified by anorexics as a girl named 'Ana'. The lesser-used term pro-mia refers likewise to bulimia nervosa and is sometimes used interchangeably with pro-ana.
Pro-ana organizations differ widely in their stances. Most claim that they exist mainly as a non-judgemental environment for anorexics; a place to turn to, to discuss their illness, and to support those who choose to enter recovery. Others deny anorexia nervosa is a mental illness and claim instead that it is a "lifestyle choice" that should be respected by doctors and family.
The scientific community recognises anorexia nervosa as a serious illness. Some research suggests anorexia nervosa has the highest rate of mortality of any psychological disorder.