The definition of a single word can turn a case, and courts are often stumped with slang. "Slang has always been a challenge for the courts in cases that involve vulgar or insulting language. Conventional dictionaries lag the spoken word by design. That has lawyers and judges turning to a more fluid source of definitions: Urban Dictionary, a crowdsourced collection of slang words on the Internet."
As noted, traditional dictionaries are often behind when it comes to slang terms. "It can take years for slang terms to be included in traditional dictionaries, whose editors want to be certain that the words have staying power. By contrast, some new words rush into Urban Dictionary in less than a day. As a result, the site has cropped up in dozens of court cases in recent years."
In fact, "[i]n the last year alone, [Urban Dictionary] was used by courts to define iron (“handgun”); catfishing (“the phenomenon of Internet predators that fabricate online identities”); dap (“the knocking of fists together as a greeting, or form of respect”); and grenade (“the solitary ugly girl always found with a group of hotties”)."
We're starting to see more of a reliance on Wikipedia and other crowdsourced sites. So much so that "St. John’s University in Queens published an article that tried to create standardized rules for the most appropriate uses of crowdsourced Web sites."
Critics call these resources the lazy-man's resource, but often, these types of resources are the only authority available. I've used Urban Dictionary enough to know how useful it can be when dealing with popular slang, but it is important to realize that it is just one interpretation. Urban Dictionary can be used as one authority, but courts should refer to many authorities before settling on the definition of a word that is important to a particular issue.