It begins, as it always does, with a song. A particular song, which ruined the English-speaking world on what was probably always-already a ruined concept. The concept: Irony. The song: Ironic, by that chanteuse of the north country, Alanis Morisette.
Let us use as our working definition the following:
1) The use of words to express something different from and often opposite to their literal meaning – and, to a lesser degree, 2) Incongruity between what might be expected and what actually occurs.
Working with the first (primary) definition, I suggest that the following are not instances of irony:
- Encountering a person about whom you have recent been thinking or speaking. (This is merely a coincidence – plus, this has nothing to do with language, necessarily, and it is important to note that irony is a figure-of-speech, that is, a poetic or rhetorical device.)
- Receiving a good grade on a test for which one did not prepare, or on a paper on which one spent minimal time and effort. (This is an example of good luck that might be described as odd – one might argue that the second [lesser] definition applies here, but I say No.)
- Most jokes. (These might be funny, strangely funny, even absurd, but probably not ironic.)
To end on a positive note, I submit the following as examples of certifiable irony:
- Complaining about something by saying the opposite of what you really mean, e.g. “I love these new astronomical fuel prices!”
- When President Bush says he supports a “culture of life,” and that we should always “err on the side of life.”
- This picture.
Finally, it ends, as it always ends, with a song. The best lyrical-musical example of irony I can think of, at this moment, is Simon and Garfunkel’s “I am a Rock” – wherein the narrator, describing his sad and lonely, love-lost condition, sings “If I’d never loved / I never would have cried / I am a rock / I am island.”
(Please post as “comments” your own real-life examples of irony.)
 I am blatantly ripping off Dave Eggers’ tirade about the (ab)use of irony, which can be found on pp. 33-35 of Mistakes We Knew We Were Making, the “addendum” to the 2nd edition of A Heartbreaking Work of Staggering Genius (New York: Vintage, 2001). Also, I intend a duplicitous meaning of dis-contents – that is, “absence of contentment” and also “absence of content(s) [i.e. meaning].” However, my pointing this out in a rather meta-critical or post-modern, self-reflexive mode is in no way ironic.
 I will not belabour this point, as most have perhaps (one hopes) unpacked the internal inconsistency (incoherence, really) of this song. The events and situations described therein are not, in any way whatsoever, ironic. A fly in one’s chardonnay? 10,000 spoons when the task (eating, one assumes) one is about requires merely a knife? Rain on one’s wedding day? These things are not, and never have been, ironic. They are infuriating. They are tragic, perhaps, or even oddly humorous when viewed with a certain level of remove, or coincidentally dissonant when the reality is held up against the ideal. But they do not fall within the category of irony. They simply and undoubtedly suck.
The only situations described in the song that might be considered ironic are: stepping outside for a cigarette (expectation? I’ll be able to have a smoke.) only to notice a “No Smoking” sign (reality? Alas…), and encountering the person of one’s dreams (expectation? This is the One!) only to be introduced to that person’s spouse (reality? Swing and a miss). But, as these only marginally fall within the second (lesser) category of irony (who can say what one’s expectation is, anyway?), they can easily be dismissed as cases in which the songwriter accidentally and coincidentally (but not very ironically) stumbled upon a situation that actually is somewhat ironic in the midst of sundry situations which are not. However, I am not the first to point out that it is certainly ironic that a song entitled “Ironic” should be so devoid of ironic content.
 One might immediately think that this second definition would justify “a free ride when you’ve already paid” as a viable instance of irony, but in fact, it still is not. Why would one expect a free ride, especially when one has already paid? I stand by my original claim that this is dissonance between reality and ideal (not ironic), not incongruity between reality and expectation (ironic…sort of). And the story of the unfortunate chap who, after finally mustering the courage to travel by air, dies in a plane crash? That’s not ironic (despite what our aforementioned exegete says here). That’s not even humorous, when viewed from any perspective. It’s rather sad: the guy is dead – and the song even says he “kissed his kids goodby-ee-eye,” which intensifies the sense of tragedy.
 However, if one had an essay assignment (e.g. “Trace the development of the concept of the Self from St. Augustine to the current debates about ‘post-humanism’, taking particular account of the contributions of Eastern thought [chiefly Buddhism]”), and one handed in a paper, handwritten, containing only the statement, “I worked very hard on this essay,” this would certainly be an ironic statement. And if the professor returned that essay with the phrase, written in red pen, no doubt, “And for this, I have given you an excellent grade,” this too (provided the professor didn’t actually award one’s lack of effort with a high grade, perhaps to make a point about grace or some such thing) would likely be a case of irony.
 Sarcasm is a form of irony. However, in such statements, irony is usually eclipsed by sarcasm, and lost. Furthermore, overstatement, hyperbole and understatement are forms or subcategories of irony. When making such statements, if one is met with the question, “Are you just being ironic?”, one should not be confused by the question (wondering if in fact the questioner meant “sarcastic”) and answer, “Yes.”
 As Dave Eggers’ points out, footnotes are not ironic. I would add: Neither is the use of italics. Or sentence fragments. And definitely not hyperlinks, which are unnecessary and should be avoided.