this is a jamaican word was not originated in london but is use frequently by londoners. this word is is the america equivalent to "oh shit". it is an exclamation that is used when something suprising happens.
for example: rahted! where did that car come from
rahted that guy jus got knocked the fuck out
or rahted that guy jus got shot for saying rahted originated in london when it came from jamaica to rahted!
London slang. exclamation, meaning similar to like 'wow' or sum shit like that. expressing surprise.