[1] The site was founded in 1999 by Aaron Peckham while he was a freshman computer science major at California Polytechnic State University, San Luis Obispo.

He had previously created a spoof version of the Ask Jeeves web search engine while studying at Cal Poly but closed the website after he received an infringement letter.

In 2003, the website gained wider attention after a news article revealed that a judge of the High Court of Justice in the United Kingdom had used Urban Dictionary to assist interpreting slang lyrics in a case involving two rappers.

"[7] The website was later referenced in a 2011 District Court complaint by Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) agents to document the meaning of the vulgarism "murk", as used in a criminal threat.

Urban Dictionary has been criticized for hosting and failing to remove offensive submissions, including ones containing racist and sexist content.

[13] Urban Dictionary's guidelines list "hate speech, bullying, or any other statements meant to discriminate or incite violence against others" as a reportable offense.

"[16] Urban Dictionary was also used in a District Court complaint where a man posted a threat on a gun exchange Facebook page to "murk that cocksucker".

For example, a man in Las Vegas was allowed to keep "HOE" as his license plate after managing to convince the state, with the use of Urban Dictionary, that it meant "TAHOE", as in the vehicle made by Chevrolet, since that was already taken.

After having all the words and definitions incorporated into Watson, it began responding to researchers' questions with profanity, leading the programmers to remove it from its memory and adding another filter to prevent it from swearing in the future.

[17] In August 2019, the Malacañang Palace reacted to definitions of Philippine President Rodrigo Duterte's last name on the site; defining 'duterte' as "deceptive, sly, fake" and, "that leftover shit that you wipe off your anus after pooping."

[18] Linguists continue to use Urban Dictionary for charting the development of slang terms, particularly those from the early 2000s before the advent of many social media platforms.