1 /ˈmidiə/ [mee-dee-uh]
1. a pl. of medium.
2. (usually used with a plural verb) the means of communication, as radio and television, newspapers, and magazines, that reach or influence people widely: The media are covering the speech tonight.
Means of communication that reach people widely could refer to pretty much anything. The telephone isn't a medium in this sense, as it is a one-to-one communication device. Media that can be one to one or one to many at the same time are basically anything on the internet, but it is an action - the action of uploading, repurposing, sharing, etc, that gives them their influence. Media have stopped being a place or a destination, and become an action.
(and don't get me started on the usually used with a plural verb!)
HT to John, who was talking about some other noun/verb confusion the other day)