1. Term used to describe when something is operating, but is not being used. For example, when your computer is on, but you are not doing anything with it, it is idle. Today, when a computer or electronics device is idle for too long it may go into an energy conserving mode or standby to save power.
3. When referring to chat, an idle user (idlers) refers to someone who is logged into the chat, but hasn't been actively chatting for several minutes. Often these are users who're away doing other things such as eating or sleeping, but want to remain on to view the conversations that happened while they were gone.
4. Alternative abbreviation sometimes used for IDE (Integrated Development Environment).