Premature ejaculation is likely the most common sexual dysfunction in men with a worldwide prevalence of approximately 30%. Epidemiological studies, accurate diagnosis, appropriate treatment and evaluation of clinical trials need a universally acknowledged definition that is also capable of operationalization. Studies have defined premature ejaculation differently. The most widely used definition is the DSM-IV-TR definition. However, the majority of these definitions are authority-based rather than evidence-based, and has no support from clinical and/or epidemiological studies. In this article, 41 articles were examined, various definitions of premature ejaculation were reviewed, definition criteria of it were discussed and classification of this dysfunction was mentioned. The results showed that multidimensional classifications and definitions using various diagnostic criteria, especially objective criteria like IELT are the most appropriate ones.