Irony (n): an outcome of events contrary to what was, or might have been, expected.
Example, when evangelical Media appostle, anti-gay, ultra-conservative Ted Haggard's homesexual prostitue steps forward and outs his drug abuse... that is absolute irony and thusly hilarious. The shit that makes you laugh, Mr Pat, is stupid and a reflection of the lack of intelligence it would take to think it as something more.