No, trust me, irony is saying the opposite to what you mean in an obvious way. It's a way of speaking that can be used sarcastically, but it's not identical with sarcasm. You can be sarcastic in other ways, too, because sarcasm just means adopting a mocking tone, and you can do that without using irony. And, similarly, you can be ironic without being sarcastic, as varwnos was (he wasn't being sarcastic, because he wasn't being genuinely rude or scornful of the unit).
The word "irony" is often applied to situations like the one you describe because there's an incongruity involved, which is rather like saying the opposite to what you mean. But that's not really the base meaning of the word.
And now I'm going to go and stop being OT!
The word "irony" is often applied to situations like the one you describe because there's an incongruity involved, which is rather like saying the opposite to what you mean. But that's not really the base meaning of the word.
And now I'm going to go and stop being OT!
... well, eventually yes, but at the moment 
