An oxymoron is a conjoined pair of (seemingly) contradictory terms, e.g.
deafening silence, pretty ugly, same difference, silent scream, or jumbo shrimp. The pairing, while apparently paradoxical, will usually have a coherent meaning.
Also, you can think of an oxymoron as a contradiction or paradoxical phrase used intentionally for rhetorical affect. It consists usually of two words normally considered impossible to connect. Examples might be "tough love", "sometimes you must be cruel to be kind", or this, from the link below:
Tennyson's Idylls of the King contains two oxymorons:
"And faith unfaithful kept him falsely true"
An oxymoron used as a figure of speech would be "lead balloon" (a misguided effort or creation). Although it is possible to make a lead balloon, it would almost certainly not function as a balloon.
(see related question and links)
An oxymoron is 2 words put together that do not match. eg. fuel-efficient Hummer
A group of word that are opposite.
EXAMPLES:
JUMBO SHRIMP
CLEAN DUMPSTER
HATER OF LOVE