In football terminology, Big Uglies refer to the offensive and defensive linemen...the players who bang into each other on every play, and ostensibly work harder, aka "uglier," than more glamor positions like quarterback, wide receiver, or cornerback. The term has a similar meaning in finance.
The world of Wall Street regards the big uglies as the boring, long-standing industrial conglomerates. The companies get the work done, making steel, generating electricity, or mining iron, but don't generate a lot of media profiles, like the sexy high-growth tech firms do.
The general idea in both the football and finance scenarios is that the Big Uglies are often ignored, because they are a ton of work to financially model; they aren't flashy. They just...are. Ugly.