A) Literally "wave motion fist," the hadouken is a special move utilized by the likes of Ryu, Ken Masters, Akuma, Sakura Kasugano, and Gouken. It is executed through channeling the ki into your fists and releasing it into a ball of energy from there. Dan Hibiki has a weaker variant of this move, called the Gadouken, literally "self taught fist." QCF+P!
B) Some lame rock band from England that couldn't come up with an original name.
a) Spam Hadoukens, Win Game
Ken: Hi, Ryu!
Ryu: HOW DOOO, KEN!
HOW DOOO, KEN!
b) Don: There's a band named "Hadouken?" That's sweet!
Belle: Hell no, that's lame. I suppose now there'll be other bands called "Shoryuken
!" or "I'dLikeSomePoundCake
!" or however the hell that last one is pronounced.