Definition:  The use of words to convey a meaning opposite of its literal meaning; sarcasm.

Example from The Pearl:  Kino says, "'[Coyotito] will go to school'" (p.25).  At the end of the story, Coyotito dies.

Example by me:  She said, "You are so smart, you will go to college," to the dumbest kid in school.  He ended up dropping out of high school.