so, what exactly is an oxymoron?

Oxymoron is a figure of speech in which incongruous or contradictory terms appear side by side; a compressed paradox.

The original oxymoron is "sweet and sour" (oxy = acid, sharp and moron = sweet, soft) -- nowadays "bittersweet" is more common. Anything that looks contradictory or paradoxical but is true; "a contradiction in terms" means that one part or other is likely to be untrue.

Take for instance: "The bulldog is pretty ugly as compared to other breeds." The phrase "pretty ugly" here is an oxymoron. How can something be pretty and ugly at the same time? Pretty means attractive. It also is used as an intensifier to indicate a moderately large amount, as in “He is pretty hungry/tired/excited, etc.” When it is used in the second sense, but juxtaposed to a word that contradicts the first sense, we are aware of both senses at once, and an oxymoron results. Awfully pretty is the same thing in reverse.

Get it?