Plug-ugly means extremely unattractive. Plug-ugly sometimes refers to a villain, a thug. The word plug-ugly is derived from the name of a Baltimore gang in the 1850s, the Plug Uglies. This gang took part in numerous politically-motivated riots during the 1850s and 1860s. It is believed that the Plug Uglies took their name from the plug hats that they wore. In popular slang of the day, plug was a term for a homely, average person, perhaps partially accounting for the term. Today, plug-ugly is spelled with lowercase letters and hyphenated, whether used as a noun or an adjective. Plug-ugly is mostly an American term.
Pug-ugly also means extremely unattractive, it is mostly a British English term. Pug-ugly was first used at about the same time as plug-ugly, the word pug is derived from the word pugilist which means a professional boxer.
Unlike Frazier or Liston, Mr. Ali was nothing like the classic plug-ugly prizefighter. (The Boston Globe)
Cinderella star Lily James faces way more than just a pair of plug-ugly sisters as she switches to the role of Elizabeth Bennet in this blood-splatteredly bonkers take on Jane Austen’s famous novel, set in a 19th century England overrun with the undead. (The Daily Star)
So the complaints of bullying by Putin’s plug-ugly maniacs have a slightly hollow ring, you know? (The Sun)
In normal circumstances, few would lament the passing of a pug-ugly multi-storey car park scheduled for demolition. (The Guardian)
It is as plain as the busted nose on an open-side flanker’s pug-ugly visage that Itoje will be a red-rose regular before the year is out, so there is no burning need to rush him into a difficult match at a stadium that frequently doubles as a graveyard when England are in town. (The Independent)