Definitions of typosquatting
the act of registering domain names (=the part of an email or website address that shows the name of the person, company or institution etc that owns that internet address) that are based on spelling mistakes the user makes when entering another domain name. Typosquatting is a type of online fraud based on the assumption that people are predictably bad at spelling.
The Facebook case is by no means the first case of typosquatting to occur, but it has arguably been the most publicized.