I agreed with the definition the guy said for the words Otaku, Moe, Cosplay, and Burikko, but totally disagree on the definition of Tsundere.
The guy explained that it is when you say something meanful when you don't really mean because you are shy. However, I think Tsundere is the action when one person usually acts mean but rarely expresses love or show nice attitudes to the others. Connecting with other words, when someone treats you "Tsundere-ly", that is the time you get "Moe" feeling.
