Imagine that you are joking about something, but so much that you no longer know whether you are joking or serious. This is post-irony. It occurs when irony becomes so deep that the boundary between joke and truth becomes blurred.
Let's start with the simple: what is irony? Imagine that you bring an umbrella, but it’s bright and sunny outside. And you say, “What a great weather for an umbrella!”. This is irony — when your words say one thing, but what is actually meant is something else.
Post-irony goes further. For example, you wear a shirt with a silly slogan that you supposedly don’t like. At first, you wear it as a joke (irony), but then you wear it all the time, and it’s no longer clear whether you are joking or if you actually like it (post-irony).
Meta-irony is when you are joking about the joke itself. It’s like you realize that even a post-ironic joke can be interpreted in different ways, and you start to play with this multilayeredness. In everyday life, for example, you say that you will be “relaxing” at work, meaning both a joke and the truth at the same time. Post-irony in this case makes your statement even more confusing, but at the same time funny and sharp.