1. A situation where the result is a complete reverse (and practical mockery) of what was expected
2. A word heavy misused and abused in conversation today, mostly by people who think that using the word in any way will automatically make them seem intelligent. The word is usually misused to exactly mean "coincidental" or "tragic", when again it doesn't mean this (see #1)
If the heavy metal band Anthrax dies of anthrax, that would be poetically tragic, but not ironic. If a diabetic crosses the street and is run over by a truck carrying insulin, then it's ironic.
"Isn't it ironic that the pop song 'Ironic' contains absolutely no examples of irony?"
"One issue of Mad Magazine showed Alfred E. Neuman face-down in the desert, crushed to death by a parachuted crate of first aid supplies. Now THAT was ironic!"
-the opposite of the literal meaning
-a mismatch between the expected and the actual result
pro-lifers making death threats to Michael Schiavo is ironic
That a song about things which are ironic makes no mention of any things which are, in fact, ironic.
When a hipster has a guilty pleasure they want to publicly partake in, and is pretending not to genuinely enjoy it.
Steve proudly wore his pink Backstreet Boys T-shirt, knowing that his hipster friends would think he was wearing it ironically. He took it even further by posting three whole facebook albums of the concert he got it from.
An unfortunate event having a perverse outcome in the particular context.
Publishing an incorrect example of "ironic" on urban dictionary. For example" "rain on your wedding day" is not ironic. That is unfortunate. It would be ironic if you were a weatherman who predicted sunshine on your wedding day. But, that would be tough to sell as a lyric.
Something is Ironic when what happens is the opposite of what is expected
It is ironic that Perez Hilton called Will.I.Am a faggot because Perez is gay.
a) Something that is contradictory.
b) Something that is complete and utter bullshit (but often accepted nonetheless.)