"Irony (from the Ancient Greek εἰρωνεία eirōneía, meaning hypocrisy, deception, or feigned ignorance) is a literary or rhetorical device, in which there is an incongruity or discordance between what one says or does and what one means or what is generally understood." (Definition from Wikipedia)
Or simply its meant the use of words to express or convey something different from and often opposite to its literal meaning, and we got a very good example to show u guys what is Irony meant btw (see below):
Info.cern.ch was the address of the world's first-ever web site and web server, running on a NeXT computer at CERN. The first web page address was http://info.cern.ch/hypertext/WWW/TheProject.html, made by Tim Berners-Lee.
Today we got a special logo on Malaysia google home page, so whats the special on that? guess? try to guess.. for those are malaysian, most probably ure know today is our national day aka Hari Merdeka right? but dont u remember how old are 'we' the malaysia already? It was.. 52 years old! Juz half a century as old as for some malaysians who are borned on 50s : )