noun

• (video games, online gaming) Acronym of multi-user dungeon, an interactive online environment in which players may jointly engage in fantasy role-playing games.

name

• (Venezuelan politics) Democratic Unity Roundtable, a coalition of opposition political parties in Venezuela.
  "The local branch of the ruling United Socialist Party (PSUV) announced its intention to disrupt the MUD rally at a press conference the day before; municipal vehicles were laid on to take the chavistas out there."

noun

• (slang, construction) Wet concrete as it is being mixed, delivered and poured.
• (figuratively) Willfully abusive, even slanderous remarks or claims, notably between political opponents.
  "The campaign issues got lost in all the mud from both parties."
• (slang) Money, dough, especially when proceeding from dirty business.
• (gay sex, slang) Stool that is exposed as a result of anal sex.

verb

• (transitive) To make muddy or dirty; to apply mud to (something).
• (transitive) To make turbid.
• (intransitive) To go under the mud, as an eel does.