(n.) A typically short combination of letters used together when an attention-loving internet user takes a commonly used phrase and abbreviates it for no reason and posts it on Urban Dictionary. The abbreviation usually does not even create an acronym and it is unlikely that anyone would understand what the abbreviation meant if it was used in any context what-so-ever.
While scrolling through Urban Dictionary last night I saw the newest of the useless Urban-abbreviations on the front page. A user decided they should post that lbd
(an abbreviation for "little black dress") on the site, thus filling a spot on the page with useless garbage that doesn't need to be said.