My understanding of irony comes from the movie "Reality Bites":
It's when the actual meaning is the complete opposite from the literal meaning
Frequently people use the term incorrectly, applying it where the actual meaning and the literal meaning are surprisingly similar in unintended ways.
A perfect example of the incorrect usage is the picture below.
It's definitely not irony, so what word can we use?
(Just in case the link has broken, it's a picture of a building with a plaque saying "George Orwell Lived Here". Pointing out in front of the building is a security camera.)