Someone who initially appears intelligent but is found to act idiotic in the majority of situations.
A Niddy will - act without thinking
Ask the same question more than twice
Not be able to see something directly in front of them
Have a terrible memory
Be extremely clumsy
Think that sarcasm is wit
Under no circumstances can a Niddy multitask nor even think and speak at the same time.
Can also be used as an alternative monika for males named 'Christian'.
"OMG, he's such a Niddy! Even though it's cleary written on the packet and I explained it to him 6 times, he's still eaten the bar of laxative chocolate! Niddy!"