Sometimes I see people write "mimimi" in AFD tweets (for example this). Googling for the meaning wasn't useful.
So, what is the meaning of "mimimi"?
I even discovered the #mimimi hashtag, used in other languages. Not sure if it matters.
Did you really check carefully? The most complete answer is found here:
In short: someone who uses the term wants to express that the author (who is complaining about something) is whining or exaggerating and he should not be so sensitive or so touchy. So then you simply say:
Mimimi. Jammer nicht so rum.
A rude form would be:
"Mimimi" has its origin in the Muppet Show, where the assistant Beaker only says this in high pitch and always shortly before panic.
This was adapted, always in high pitch, to demonstrate that one has no pity with his counterpart.
The "mimimi" itself is the sound of wailing, so it is an onomatopoeia.
I would like to provide a different insight.
I am Brazilian, and I'm very used to the expression "mimimi". It's a slang widely accepted among teenagers in Brazil, and interestingly it has basically the same meaning provided in the answer by Thomas. I would describe it as an onomatopoeia that pejoratively represents the words/sounds a person makes when complaining. You usually refer to someone's complaints as "mimimi" when you disagree with them and consider the complaints unfounded, merely as a gratuitous hating towards the subject.
Example: "Oh, the daylight saving time is here, so here comes the mimimi". (Meaning that here comes a bunch of people complain gratuitously about it without really thinking about it).
I never stopped to think about where this originated from, so I got extremely curious when I saw this on German SE ("what does German have to do with this?", I thought), and amazed with the answers referring to what seems to be a muppet show or something.
After some cursory search with Google already biased to give me Brazilian results, what I found is some sites claiming that the expression originated from a Brazilian TV show "Fudêncio e Seus Amigos" (a politically incorrect show from the channel MTV).
I'm not saying the other answers are wrong, I just wanted to share this because it can't just be a coincidence.
Also this probably addresses what OP said as #mimimi hashtag usage in other languages (I bet it's Portuguese!)
It's used to mock a person that is always complaining. The "mimimi" stands for the wailing of that person. "Mimimimi" itself holds no meaning. I think shows that the wailing of that person is either unnecessary or exaggerated, or perhaps even almost a character trait. It also sort of mimics the sound of a crying baby.
"mimimi" is just like a disliking symbol, when someone do some work which was not expected and there is benefit then the person does some murmuring sound like this by himself.
By some research I found:
1.Child's weeping. This meaning is the original and was inspired by the Mexican TV show "El Chavo del Ocho", which was a massive success in Brazil.
2.Emotional, childish or sissy begging: "He wasn't hired for the job and started with mimimi that his mother was ill and he needed the money to treat her."
3. Stubborn irrational refusal to accept what is plainly true. Eg: "Germany deservedly won the 2014 World Cup. Any other opinion is mimimi."
4. Annoying complaint about something that could have been solved more maturely. E.g: "The manager told him that he had been a relapse worker recently and should improve. Instead of accepting that feedback he just went on mimimi about how cruel and insensitive the manager was."
This is not originally German or Muppetese. Minimi is Latin for "things of no importance". It's most often seen in the well known legal saying De minimis non curat lex (the law doesn't care about things of no importance). So to call people or things minimi is to call them insignificant.