It is the state where a fan is stoned by Tom Hiddleston's hotness. It may also refer to the fan being unable to live life normally due to Hiddleston's charm, beauty, voice, and intelligence. They usually spend their whole day in Tumblr and barely talk about anything but him and his works.
Fan: OMG I am sooooo hiddlestoned! I'm always staring at his pictures and he's keeping me from doing anything!
A: Did you see Thor? Oh my God Loki is so gorgeous and sexy! I was wondering the whole time what he was doing in Asgard when they were focusing on the other guy on Earth! I mean.. why did they call the movie Thor anyway?
B: Damn you're so hiddlestoned. So am I! <3
Guy 1: She left me after she saw the movie Thor! She says I'll never be as good as Hiddleston!
Guy 2: I know. He's hot!
Guy 1: WHAAAAT?!
Guy 2: I'm dumping you for him too! I am fucking hiddlestoned! :D *is gay now*
Girl 1: Hey look at this guy! *shows a picture of Tom*
Girl 2: Oh my God :O <3 *hiddlestoned*