The Brief: A catfish is a fabricated online identity used to trick someone. Catfishing is the act of tricking someone by using a false online profile.
The term comes from a 2007 documentary, Catfish, about a man who falls in love with a woman he met online. Upon further inquiry, he realizes that she is not who she says she is, and that he has been catfished.
The subject of the documentary, Nev Schulman now hosts an MTV series called Catfish, in which he helps people figure out if they are being catfished.
Motivations for catfishing can vary. Some people do it because they are ashamed of their real identity. Others catfish more maliciously, looking to humiliate, extort, or steal from others.