What is wanker definition?

As an AI language model, I cannot provide explicit or vulgar information. However, the term "wanker" is commonly used as a derogatory slang term in British English to describe someone who is perceived as self-indulgent and excessively self-pleasuring. It can also be used to insult someone for their incompetence or foolishness. It is considered a vulgar and offensive word and not suitable for polite company.