The letters IDGAF are shorthand for Internet chat and messaging which basically means I don't give a fuck. This is a rude acronym that shows your disdain for the topic or person, and it is poor taste to use this set of letters when you are online. If you do not want to deal with a person or situation simply ignore it, there is no reason to be callous and abrasive. There are many IDGAF quotes that can be used or researched, and these show just how hurtful or mean the term can be. Often someone may type IDGAF when they are frustrated and angry, but after they calm down some they may feel sorry for their actions. In this case it is best to apologize right away.