eu·phe·mism –(noun)
Examples: "Heavy set" vs. fat
"to pass away" vs. to die
"rest room" vs toilet
1 : a pretense of ignorance and of willingness to learn from another assumed in order to make the other's false conceptions conspicuous by adroit questioning —called also Socratic irony
2 a : the use of words to express something other than and especially the opposite of the literal meaning b : a usually humorous or sardonic literary style or form characterized by irony c : an ironic expression or utterance
3 a (1) : incongruity between the actual result of a sequence of events and the normal or expected result (2) : an event or result marked by such incongruity b : incongruity between a situation developed in a drama and the accompanying words or actions that is understood by the audience but not by the characters in the play —called also dramatic irony, tragic irony
ex. It was ironic that Reagan was shot after the bullet ricocheted off of his "bulletproof" car.
Source: Merriam-Webster Online Dictionary