An Oxymoron is a combination of contradictory or incongruous words, such as 'Cruel Kindness' or 'Jumbo Shrimp' (Jumbo means 'large' while Shrimp means 'small').

It is a literary figure of speech in which opposite or contradictory words, terms, phrases or ideas are combined to create a rhetorical effect by paradoxical means.

The word 'Oxymoron' is originally derived from the Greek elements: oxy = sharp and moros (moron) = dull (foolish). 'Oxymoron' is the singular form, and 'Oxymora' (or 'Oxymorons') is the plural form.

Some Oxymorons are not obvious, some may require an understanding of verbal or regional interpretations, and some may even indicate certain prejudices.

Oxymorons are not necessarily mistakes or errors. They make effective titles and appealing phrases, and some are meant to be humorous.

'Oxymoron' as defined on Dictionary.com