/ ˈsɑːkæzəm; NAmE ˈsɑːrk-/ noun
[ U ] a way of using words that are the opposite of what you mean in order to be unpleasant to sb or to make fun of them :
'That will be useful,' she snapped with heavy sarcasm (= she really thought it would not be useful at all) .
a hint / touch / trace of sarcasm in his voice
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WORD ORIGIN
mid 16th cent.: from French sarcasme , or via late Latin from late Greek sarkasmos , from Greek sarkazein tear flesh, in late Greek gnash the teeth, speak bitterly (from sarx , sark- flesh).