It's the chemical name of titin. It takes 3 and a half hours to read.

See the whole word here: http://pastebin.com/wkKH8xD8

io9: "Okay, technically the 189,819-letter IUPAC name of titin, the largest known protein which is responsible for passive elasticity of muscle, is a verbal formula rather than an actual word, but it's dizzying to imagine all those syllables tumbling out of a human mouth. Well, now you don't have to imagine it—provided you can sit through more than three hours of this fellow mumbling his seryls and glutamins."

SPOILER ALERT!

It's freakin hilarious!  

The plant slowly dies throughout the whole thing but the end is the best part... and at the end he gets up right before (presumably) the last few syllables because somebody is coughing in the background and disturbing the sound quality...hah!

If you're going to spend 210 minutes on an activity like this, it helps to have a sense of humor about it. :)