Something that is so intensely amazing or spectacular that it can't be described by words. It causes one's mind to collapse inward on itself due to the sheer awesomeness.
Pete: Hey dude check out my tricked out ride!
Paul: Damn bro this thing is head-imploding!
Dan: Yo dude you won't believe this, but last night my girl was frisky and I became a man; I am a virgin no more.
Rob: Nice dude, how was it?
Dan: One word: Head-imploding