It is a testament to the sophistication of Western languages that they have a word for irony. None of the Middle Eastern languages I know (Hawrami, Kurdish, Farsi, Arabic) have a word for it. Farsi has wārūneh gūyī (literally “saying the opposite of what is meant”), but this refers to sarcasm and unintended ironical statements.

Below are all examples of irony:

Her heart was as soft as a brick.

She spent years working hard to be a novelist until she gained worldwide renown for winning a poetry prize.

The fire station caught fire.

A serial killer became the victim of a serial killer.

"Let's meet for coffee tomorrow," he said, while the audience knew he would be dead by the evening. [tragic irony]

"My wife is dragging me to this play. Someone please kill me," Abraham Lincoln tweeted.

Someone drank from the Fountain of Youth and died, not knowing that the water had to be boiled first. [from Terry Pratchett's Eric]

What is the thing about all of these that makes them ironical?

Looking up irony on Wikipedia, I saw this:

Henry Watson Fowler, in The King's English, says, "any definition of irony—though hundreds might be given, and very few of them would be accepted—must include this, that the surface meaning and the underlying meaning of what is said are not the same." Also, Eric Partridge, in Usage and Abusage, writes that "Irony consists in stating the contrary of what is meant."

I wasn’t satisfied by any of the definitions of irony given in the Wikipedia article. Meditating on the question, I realized that the problem with defining irony is that linguists expect to find the meaning of irony within the structure of the ironical sentence, image or scene. But I realized that irony is actually a psychological phenomenon:

Irony is anything that attempts to pull your leg by making you expect a certain meaning, giving you a sense of smug self-satisfaction when you recognize the snare and you see the wider meaning.

Irony pulls you in, giving you pleasure when you mentally “pull out”. Thus “as soft as a brick” is ironic because “as soft as” sets you up to expect a proper simile. Once you realize the comparison is with a brick, you mentally pull out of the set up and realize what is going on. This gives you a nice “sense of pride and accomplishment”, as the Electronic Arts spokesperson said.

The fire station being on fire is ironical because the mundane interpretation is that it is just a building on fire. But once you mentally pull out and recognize the wider context, you see the incongruity between a building meant for fighting fire actually being on fire.

Anything ironical has therefore a mundane or naive interpretation (a serial killer is dead) and a wise or wary interpretation (a serial killer is dead by his own category of crime). It is the mental leap from the naive to the wise interpretation that gives us the pleasure of irony.

Tragic irony, as in someone likable in a novel saying “See you tomorrow!” while the author has told us the person is going to die before the day’s end, is the same kind of setup. The difference is that due to feeling sorry for the character, we stop ourselves from feeling the usual smug self-satisfaction at our mental leap. But if we wanted to be unkind, then it would give us exactly the same kind of pleasure as any other kind of irony, as in laughing at Abraham Lincoln’s imaginary tweet asking to be killed.

To give a more technical definition:

Irony is anything that sets you up for a naive interpretation, giving you pleasure when you mentally leap to the wise interpretation.