Despite what the other definitions on here say, a person who catfishes online is not a catfish. The term "catfishing" (online) derives from real-world fishing. The person who is catfishing puts the bait out there, and waits for someone to bite. The person who falls for the bait and believes the catfisher is the catfish.
I love to catfish for hot girls so I can break their stupid catfish hearts.