Oxymorons or oxymora are literary figures of speech usually composed of a pair of neighboring contradictory words (often within a sentence). However this is not always the case. The Webster Dictionary defines oxymoron as ‘a combination of contradictory or incongruous words’.
The word oxymoron (plural: oxymora or oxymorons) is derived from the Greek for pointedly foolish (oxys = SHARP, KEEN + moros = FOOLISH).
Oxymorons can be used for dramatic effect, for example: ‘Hell’s Angels’ and ‘deafening silence’. They can also be comical, such as in ‘civil engineer’. Clearly this is not an oxymoron in the true and strict sense, but the suggestion that it is oxymoronic is humorous.
Perhaps the most well-known of all oxymorons is Jumbo Shrimp (at least in the US).
Others have quite acceptable meaningful uses in English, but, when analyzed word for word, contain contradictions. Examples include ‘almost perfect’, ‘clearly misunderstood’, and ‘pretty ugly’. These are only oxymorons in a punning sense.