Time Warner Cable (which was bought by Charter and will soon be called Spectrum everywhere) has launched the TeenNick channel in high definition on their TWC TV app and website, as of this week.
The channel has been available on the app before, but only in standard definition. Many (maybe all) Time Warner Cable providers still offer the channel in SD on your TV box set. However, the HD feed is available to everyone subscribed to the channel on the TWC TV app and website.
TeenNick launched their HD feed sometime between June and September. It has so far only been nationally available on Verizon FiOS and Sling TV.