Oxymoron

So fair and foul a day I have not seen!
William Shakespeare
An oxymoron is a figure of speech that deliberately uses two contradictory ideas. This contradiction creates a paradoxical image in the reader or listener's mind that generates a new concept or meaning for the whole. Some typical oxymorons are:
a living death
sometimes you have to be cruel to be kind
a deafening silence
bitter-sweet
The Sounds of Silence (song title)
make haste slowly
he was conspicuous by his absence
Pseudo Oxymorons
In the standard meaning of oxymoron the contradiction is deliberate. However, in popular usage oxymoron is sometimes used to mean "contradiction in terms", where the contradiction is unintentional. Such expressions, unlike real oxymorons, are commonly used without any sense of paradox in everyday language, for example:
anecdotal evidence
friendly fire
pretty ugly
A common attempt at humour is to describe a certain phrase as an oxymoron, implying that the two parts of the phrase are mutually exclusive and that consequently the phrase as a whole must be nonsensical:
airline food
American culture
eco-tourism
Microsoft security
military intelligence