I gripe a lot about people using the word "irony" when they really only mean "coincidence." Sportswriters are especially bad about this, as in "ironically, the two teams have the same colors." And sometimes people use it when they're referring only to chance or luck, usually bad luck, as in "ironically, it began to rain when we arrived at the beach." To clarify the definition, I offer the following:

When you are officially forbidden to eat lunch in your office but are in the habit of doing so anyway, and your lunch is frequently a sandwich and a container of milk, and you have been using a little Mason jar for the milk, and have been concerned because it would be very easily spilled, although you have never actually spilled it, and have expressed that concern to your wife, who has procured for you a cup with a very small opening that, even if overturned, would permit only a small amount of spillage, and on the second day of using that cup, you spill milk for the first time since you moved into the office in 2004--that is irony.

If only a small amount is spilled and most of it stays on the desk and your shirt, with only a few drops actually reaching the carpet, that's luck.