Words such as badass, phat, ass-backwards and bogart have found a place in the latest edition of the Shorter Oxford English Dictionary.
The dictionary has added 3,500 words to reflect changes in speech.
Jesse Sheidlower, principal North American editor of the Shorter OED told the New York Post the dictionary is no staid, stuffy repository of the Queen's English.
He told the paper: "If a slang or other non-standard expression has enough currency it will go in.
"I don't think there's any question that terms like badass or bogart have enough currency to be included."
The word must have been used five times in sources as varied as Rolling Stonemagazine and The Wall Street Journalfor at least five years to be considered.
This explains why Internet is only now being included, though the last edition came out in 1993.
"The term internet existed in 1992, but just in technical circles," Mr Sheidlower said: "It wasn't until a year or two later that mainstream familiarity started to take off."
PA