1) Rhetorical device 
use of words in a sense opposite to literal
• (n.) The use of words in a sense opposite to their proper meaning; as when a court of justice is called a court of vengeance.
An·tiph'ra·sis noun [ Latin , from Greek ..., from ... to express by antithesis or negation.] (Rhet.) The use of words in a sense opposite to their proper meaning; as when a court of justice is called a court of vengeance . 
[n] - the use of a word in a sense opposite to its normal sense (especially in irony)
noun the use of a word in a sense opposite to its normal sense (especially in irony)
the use of a word in a sense opposite to its proper meaning.